<PAGE>   1
                               EXHIBIT 10(a)(i)

                         DEFERRED COMPENSATION AGREEMENT


THE STATE OF TEXAS   )
COUNTY OF SMITH      )


     THIS AGREEMENT is entered into by and between SOUTHSIDE STATE BANK of
Tyler, Texas, a corporation organized and existing under the laws of the State
of Texas, hereinafter called BANK, and B. G. HARTLEY, hereinafter called
EXECUTIVE, whereby it is agreed as follows:

                                   WITNESSETH:

                                       I.

     The Board of Directors of BANK have determined that the EXECUTIVE services
to the BANK since its formation as its President have been of exceptional merit
and has constituted an invaluable contribution to the general welfare of BANK
and in bringing BANK to its present status of operating efficiency. The Board of
Directors have further determined that the continued service of EXECUTIVE on
behalf of BANK is essential to the future growth and profits of BANK and it is
in the best interest of BANK to arrange terms of continued employment for
EXECUTIVE so as to reasonably assure his remaining in the employ of BANK for the
balance of his work lifetime.

                                       II.

     BANK agrees to employ EXECUTIVE in such capacity as the BANK may from time
to time determine. The EXECUTIVE will continue in the employment of BANK in such
capacity and with such duties and responsibilities as may be assigned to him,
and with such compensation as may be determined from time to time by the Board
of Directors. EXECUTIVE agrees to well and truly perform his duties and
obligations as an employee of BANK and will use his best efforts to furnish
faithful and satisfactory service to BANK.

                                      III.

     It is specifically agreed that if EXECUTIVE remains in the employment of
BANK until his permanent disability, death or retirement, whichever occurs
first, BANK agrees to pay the sum and amount of EIGHT HUNDRED THOUSAND AND
NO/100 ($800,000.00) DOLLARS, to EXECUTIVE or his surviving wife or designated
beneficiaries, as hereinafter provided. Such deferred compensation shall be
payable commencing on the 1st day of the month following the first of the
following events to occur; (1) the permanent disability of EXECUTIVE; (2) the
retirement of EXECUTIVE; or (3) the death of EXECUTIVE. For the purpose of this
agreement, total disability shall be defined as a physical or mental condition
as diagnosed by a medical doctor approved or selected by BANK, that so
incapacitates or disables EXECUTIVE that he is no longer able to perform the
duties and responsibilities assigned to EXECUTIVE and that in the opinion of
such medical doctor, such condition is permanent. Such deferred compensation,
when it commences, shall be payable as follows:

     1.   Sixty (60) equal monthly installments of Five Thousand and No/100
          ($5,000.00) Dollars each, with the first monthly installment being
          payable on the commencement date as above set forth.


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     2.   Commencing on the sixty-first (61st) month following the commencement
          date, 120 equal consecutive monthly installments of Four Thousand, One
          Hundred Sixty-Six and 67/100 ($4,166.67) Dollars.


                                       IV.

     EXECUTIVE shall have the right to name a beneficiary other than his wife
provided such designation of beneficiary be in writing and signed by EXECUTIVE
and delivered to BANK. Such designation of beneficiary may provide for
alternative beneficiary if the designated beneficiary fails to survive the
EXECUTIVE or fails to survive the term payout, as provided herein. Failure to
designate a beneficiary in accordance with the terms hereof shall be deemed an
election by EXECUTIVE that such benefits as provided herein shall go to the
surviving wife or to his surviving children, should his wife die simultaneously
or predecease him.

                                       V.

     If the EXECUTIVE should die prior to retirement, and such death is a result
of a suicide, then, in such event, the death benefits provided in this Agreement
shall not be payable unless such suicide occurs after the lapsing of any
anti-suicide provisions contained in any insurance policy purchased by BANK upon
the life of EXECUTIVE, should the BANK so elect to purchase such insurance for
its own benefit.

                                       VI.

     When used herein, except as expressly provided herein otherwise, retirement
shall be deemed an event as defined or authorized by bank under existing
personnel requirements of bank of hereinafter amended or modified.

     If for any reason other than good cause, the employment of EXECUTIVE is
terminated by BANK, such termination shall not terminate this Agreement and such
involuntary termination other than for good cause shall be deemed the same as
retirement for the purpose of this Agreement. For the purpose of this Agreement,
"good cause" shall be defined as being action or inaction equivalent to habitual
dereliction of duty, misfeasance, willful misconduct, criminal conduct, or gross
negligence.

                                      VII.

     Neither the EXECUTIVE nor any beneficiary designated by EXECUTIVE shall
have any power or right to transfer, assign, anticipate, mortgage, commute or
otherwise encumber in advance any of the benefits payable hereunder, nor shall
such benefits be subject to seizure for payment of any debts or judgment of any
of them, or be transferred by operation of law in the event of bankruptcy,
insolvency or otherwise.


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                                      VIII.

     This Deferred Compensation Agreement shall be in addition to and in lieu of
a prior Deferred Compensation Agreement dated May 14, 1979, in the amount of
THREE HUNDRED THOUSAND AND NO/100 ($300,000.00) DOLLARS.

                                       IX.

     This Agreement shall be binding upon and inure to the benefit of EXECUTIVE
and his personal representatives and the BANK and its successors and assigns.
However, it is specifically agreed that this is not a contract of employment
between the parties hereto and nothing herein shall restrict the right of the
corporation to discharge EXECUTIVE or restrict the right of EXECUTIVE to
terminate his employment.


     EXECUTED as of the 13th day of February , 1984.

ATTEST:                                    SOUTHSIDE STATE BANK


By:  /s/ ROBBIE N. EDMONSON                By:  /s/ MURPH WILSON
     ----------------------------------         --------------------------------
         ROBBIE N. EDMONSON, Senior                 MURPH WILSON,
         Vice President and Cashier                 Chairman of the Board


                                                /s/ B. G. HARTLEY
                                                --------------------------------
                                                    B. G. HARTLEY, EXECUTIVE


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                               FIRST AMENDMENT TO
                         DEFERRED COMPENSATION AGREEMENT


THE STATE OF TEXAS  )
COUNTY OF SMITH     )

     THIS AGREEMENT is entered into by and between SOUTHSIDE STATE BANK of
Tyler, Texas, a Texas banking corporation, hereinafter called BANK, and B. G.
HARTLEY, hereinafter called EXECUTIVE, whereby it is agreed as follows:

                                   WITNESSETH:

                                       I.

     BANK and EXECUTIVE has heretofore entered into a Deferred Compensation
Agreement in 1982, which has continued in full force and effect subsequent
thereto. The parties hereto desire to amend and modify such Agreement, with such
amendment to be effective immediately.

                                       II.

     In such Deferred Compensation Agreement, provided that EXECUTIVE met
certain conditions precedent, the BANK, at his permanent disability, death or
retirement, whichever occurs first, pay agreed compensation to EXECUTIVE, his
surviving wife or designated beneficiaries as the case might then be. The
parties hereto desire to eliminate, and do hereby eliminate, permanent
disability as one of the enumerated events which cause commencement of payment
of deferred compensation. All reference to disability is hereby deleted from
said Agreement. Henceforth, the only occurrence that will cause the commencement
of deferred compensation payments under the terms of such Agreement shall either
be the death or retirement of EXECUTIVE under the terms and conditions of said
Deferred Compensation Agreement.

                                      III.

     Except as amended or modified by this Amendment, the parties hereto do
reaffirm and ratify said Agreement and when construed together, this Amendment
and the original Deferred Compensation Agreement shall constitute the entire
agreement of the parties.

     EXECUTED as of the 28th day of June, 1990.

ATTEST:                              SOUTHSIDE STATE BANK


/s/ SAM DAWSON                       By:  /s/ ROBBIE N. EDMONSON
-------------------------------           -------------------------------------
    Assistant Vice President                  ROBBIE N. EDMONSON
                                              Executive Vice President

                                          /s/ B. G. HARTLEY
                                          -------------------------------------
                                              B. G. HARTLEY
                                              EXECUTIVE


<PAGE>   5





                               SECOND AMENDMENT TO
                         DEFERRED COMPENSATION AGREEMENT


THE STATE OF TEXAS   )
COUNTY OF SMITH      )


     THIS AGREEMENT is entered into by and between SOUTHSIDE BANK of Tyler,
Texas, a Texas banking corporation ("BANK"), and B. G. HARTLEY ("EXECUTIVE"),
whereby it is agreed to as follows:

                                  WITNESSETH:

                                       I.

     BANK and EXECUTIVE entered into a Deferred Compensation Agreement dated
February 13, 1984. This Deferred Compensation Agreement has been modified by the
First Amendment to Deferred Compensation Agreement dated June 28, 1990. (The
Deferred Compensation Agreement as amended by the June 28, 1990, amendment is
hereinafter referred to as the "Deferred Agreement.") The Deferred Agreement has
continued in full force and effect. BANK and EXECUTIVE desire to amend and
modify the Deferred Agreement, with such Amendment to be effective immediately.

                                       II.

     The Board of Directors of BANK has determined that it is in the BANK's best
interest to encourage EXECUTIVE to continue his employment with BANK. As such,
BANK agrees to increase the amount which EXECUTIVE is entitled to receive under
the Deferred Agreement.

                                      III.

     EXECUTIVE shall receive, in addition to all other amounts which he is
entitled to under the Deferred Agreement, a bonus hereinafter called "Deferred
Compensation Bonus."

                                       IV.

     BANK shall pay the Deferred Compensation Bonus to EXECUTIVE within 120 days
after he retires and serves in none of the following capacities: President or
Chief Executive Officer.

                                       V.

     If EXECUTIVE dies prior to his retirement, BANK shall pay the Deferred
Compensation Bonus to the personal representative of EXECUTIVE's estate within
nine (9) months of EXECUTIVE's death.

                                      VI.

     The amount of this Deferred Compensation Bonus is presently $28,581.38 and
shall increase by $28,581.38 on the 15th day of December each year provided that
EXECUTIVE is employed by BANK on said day in any of the following capacities:
President or Chief Executive Officer.


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                                      VII.

     Except as amended or modified by this Amendment, the parties hereto
reaffirm and ratify the Deferred Agreement. This amendment, the First Amendment
to Deferred Compensation Agreement, and the original Deferred Compensation
Agreement shall constitute the entire Agreement of the parties.

     EXECUTED the 15th day of December, 1994.

ATTEST:                                     SOUTHSIDE BANK



/s/ SAM DAWSON                              By:  /s/ ROBBIE N. EDMONSON
---------------------------------------          ------------------------------
    SAM DAWSON                                       ROBBIE N. EDMONSON
    Executive Vice President                         Executive Vice President

                                                     - BANK -

                                                 /s/ B. G. HARTLEY
                                                 ------------------------------
                                                     B. G. HARTLEY
                                                     EXECUTIVE

<PAGE>   7

                               THIRD AMENDMENT TO
                         DEFERRED COMPENSATION AGREEMENT


     THIS AGREEMENT is entered into by and between SOUTHSIDE BANK of Tyler,
Texas, a Texas banking corporation ("BANK"), and B. G. HARTLEY ("EXECUTIVE"),
whereby it is agreed to as follows:

                                  WITNESSETH:

                                       I.

     BANK and EXECUTIVE entered into a Deferred Compensation Agreement dated
February 13, 1984. Subsequent thereto, two Amendments to such Deferred
Compensation Agreement have been executed and are in full force and effect as of
this date. A question has arisen as to the construction of Paragraph VIII of the
Deferred Compensation Agreement dated February 13, 1984, and the purpose of this
Amendment is to clarify the intent of the parties as to such paragraph.

                                       II.

     It is the intent of the parties that the Deferred Compensation Agreement
dated February 13, 1984, replace and be in lieu of the Deferred Compensation
Agreement dated May 14, 1979, which was then in the original amount of THREE
HUNDRED THOUSAND AND NO/100 ($300,000) DOLLARS. It is not intent of the parties
that there be two Deferred Compensation Agreements for EXECUTIVE and that the
Agreement dated February 13, 1984 and the Amendments thereto represent the only
Deferred Compensation Agreement between BANK and EXECUTIVE.

     EXECUTED as of the 20th day of November, 1995.

ATTEST:                                 SOUTHSIDE BANK



/s/ ROBBIE N. EDMONSON                  By:  /s/ SAM DAWSON
------------------------------               ----------------------------------
    ROBBIE N. EDMONSON                  Name:    Sam Dawson
    Vice Chairman of the Board          Title:   Executive Vice President


                                             /s/ B. G. HARTLEY
                                             ----------------------------------
                                                 B. G. HARTLEY
                                                 Executive

<PAGE>   8


                               FOURTH AMENDMENT TO
                         DEFERRED COMPENSATION AGREEMENT


STATE OF TEXAS  )

COUNTY OF SMITH )

     This AGREEMENT is entered into by and between Southside Bank of Tyler,
Texas, a Texas banking corporation ("BANK"), and B.G. HARTLEY ("EXECUTIVE"),
whereby it is agreed as follows:

                                   WITNESSETH:

                                       I.

     BANK and EXECUTIVE entered into a Deferred Compensation Agreement dated
February 13, 1984. This Deferred Compensation Agreement has been modified by the
First Amendment to Deferred Compensation Agreement dated June 28, 1990, and was
subsequently amended with the Second Amendment to Deferred Compensation
Agreement in 1994, and was subsequently amended with the Third Amendment to
Deferred Compensation Agreement in 1995. The Deferred Compensation Agreement, as
amended, has continued in full force and effect and is continuing in full force
and effect through date of this amendment. BANK and EXECUTIVE desire to amend
and modify the Deferred Compensation Agreement, with such fourth amendment to be
effective immediately.

                                       II.

     The Board of Directors of BANK has determined that it is in the BANK's best
interest to continue to encourage EXECUTIVE to continue his employment and
association with the BANK. As such, BANK agrees to increase the amount which
EXECUTIVE is entitled to receive under the Deferred Compensation Agreement.

                                      III.

     EXECUTIVE, at the earlier of his death or retirement (as the terms are
defined in the Deferred Compensation Agreement), shall be entitled to receive an
immediate cash payment of ONE HUNDRED EIGHTY-NINE THOUSAND FOUR HUNDRED THIRTY
AND NO/100 DOLLARS ($189,430.00). Such payment shall be paid as a lump sum
within thirty (30) days following the earlier of the two dates herein
referenced.

                                       IV.

     In addition, EXECUTIVE shall be entitled to receive a lump sum amount at
retirement or death, which ever occurs first, equal to the sum of FORTY-FIVE
THOUSAND THIRTY AND NO/100 DOLLARS ($45,030.00) per year beginning with February
1, 2000 and each year thereafter until his retirement or death. The final year
installment shall be prorated if it occurs before February 1 for the year in
question.

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                                       V.

     Except as amended and modified by this Agreement, the parties hereto
reaffirm and ratify the Deferred Compensation Agreement. The liabilities of the
parties are governed by the Deferred Compensation Agreement as amended.

     EXECUTED as of the 21st day of December, 1999.

                                       SOUTHSIDE BANK



                                       By:  /s/ SAM DAWSON
                                            -----------------------------------
                                                SAM DAWSON, President


                                            /s/ B. G. HARTLEY
                                            -----------------------------------
                                                B. G. HARTLEY, Executive