<PAGE>   1
      As filed with the Securities and Exchange Commission on June 4, 1997
                                                      Registration No. 333-
--------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 --------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                      THORNBURG MORTGAGE ASSET CORPORATION
             (Exact name of registrant as specified in its charter)

           MARYLAND                                          85-0404134     
(State or other jurisdiction of                           (I.R.S. Employer)
 incorporation or organization)                          Identification No.)

          119 E. MARCY STREET
         SANTA FE, NEW MEXICO                                   87501
(Address of Principal Executive Offices)                      (Zip Code)

                              AMENDED AND RESTATED
                      1992 STOCK OPTION AND INCENTIVE PLAN
                            (Full title of the plan)

                            H. GARRETT THORNBURG, JR.
                              CHAIRMAN OF THE BOARD
                      THORNBURG MORTGAGE ASSET CORPORATION
                               119 E. MARCY STREET
                           SANTA FE, NEW MEXICO 87501
               (Name and address of agent for service of process)
                                 (505) 989-1900
          (Telephone number, including area code, of agent for service)

                The Commission is requested to send copies of all
                               communication to:

                            MICHAEL B. JEFFERS, ESQ.
                       JEFFERS, WILSON, SHAFF & FALK, LLP
                       18881 VON KARMAN AVENUE, SUITE 1400
                                IRVINE, CA 92612
                                 (714) 660-7700

                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------------
Title of securities to be registered   Amount to be           Proposed maximum             Proposed maximum            Amount of
                                        registered         offering price per share   aggregate offering price(1)  registration fee
------------------------------------------------------------------------------------------------------------------------------------
      <S>                             <C>                          <C>                      <C>                         <C>     
       Common Stock, par
      value, $.01 per share           800,000 shares               $20.00                   $16,000,000(1)              $4848.48
------------------------------------------------------------------------------------------------------------------------------------

</TABLE>

(1)      Estimated solely for purposes of calculating the registration fee
         pursuant to Rule 457(h)(1), based on the closing price of the Company's
         Common Stock.

(2)      Pursuant to Rule 429 under the Securities Act of 1933, the Prospectus
         included herein also relates to shares of Common Stock previously
         registered for sale under Registration Statement No. 33-8112, which was
         declared effective on July 1, 1994 and for which a filing fee of
         $4,741.38 was previously paid. The amount of securities being
         registered for sale, together with the 976,405 remaining securities
         registered under Registration Statement 33-8112 represent the maximum
         number of securities which are expected to be offered and sold.

--------------------------------------------------------------------------------



<PAGE>   2
                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

         The documents containing the information required by Part I (plan
information and registrant information) will be sent or given to employees as
specified by Rule 428(b)(1). Such documents need not be filed with the
Securities and Exchange Commission (the "Commission") either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424. These documents and the documents incorporated by reference in the
Registration Statement pursuant to Item 3 of Part II of this form, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The following documents filed by Thornburg Mortgage Asset Corporation,
a Maryland corporation (the "Company"), with the Commission are incorporated in
and made a part of this Registration Statement by reference, except to the
extent that any statement or information therein is modified, superseded or
replaced by a statement or information contained in any other subsequently filed
document incorporated herein by reference:

         (1)      The Company's Annual Report on Form 10-K for the fiscal year
                  ended December 31, 1996, filed on March 26, 1997;

         (2)      The Company's Quarterly Report on Form 10-Q for the quarter
                  ended March 31, 1997 filed May 5, 1997;

         (3)      The Company's Form 8-K Dated May 16, 1997

         In addition, all reports and documents filed by the Company pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act prior to filing a
post-effective amendment which indicates that all securities offered hereby have
been sold or which deregisters all securities offered hereby then remaining
unsold shall be deemed to be incorporated by reference herein and shall be
deemed to be a part hereof from the date of the filing such documents.

ITEM 4.  DESCRIPTION OF SECURITIES

         The Common Stock, par value $.01 per share, of the Company (the
"Common Stock") is registered pursuant to Section 12 of the Exchange Act, and,
therefore, the description of securities is omitted.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         The validity of shares of Common Stock issued pursuant to the 1992
Stock Option and Incentive Plan (the "Plan") has been passed upon by Jeffers,
Wilson, Shaff & Falk, LLP. Michael B. Jeffers, a partner in Jeffers, Wilson,
Shaff & Falk, LLP, is the Secretary of the Company, owns 672 shares of the
Company's Common Stock, 1% of the stock of the Manager of the Company, has been
granted options to purchase 38,941 shares of Common Stock at prices ranging from
$9.375 to $20.00 per share and holds dividend equivalent rights (DERs) for 1,811
shares of Common Stock.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Maryland General Corporation Law provides that a Maryland corporation
may indemnify any person who is or was serving at the request of the
corporation as a director, officer, partner, trustee, employee, or agent of
another foreign or domestic corporation, partnership, joint venture, trust or
other enterprise of employee benefit plan ("director"), that is made a party to
any proceeding by reason of service in that capacity unless it is established
that the act or omission of the director was material to the matter giving rise
to the proceeding, the director had reasonable cause to believe that the act or
omission was unlawful. Indemnification may be against judgments, penalties,
fines, settlements, and reasonable expenses actually incurred by the director
in connection with the proceeding, but if the proceeding was one by or in the
right of the corporation, indemnification may not be made in respect of any
proceeding in which the director shall be adjudged to be liable to the
corporation. Such indemnification may not be made unless authorized for a
specific proceeding after a determination has been made, in a manner prescribed
by law, that indemnification is permissible in the circumstances because the
director has met the applicable standard of conduct. The director must be
indemnified for expenses, however, if he has been successful in the defense of
the proceeding or as otherwise ordered by a court. The law also prescribes the
circumstances under which a corporation may advance expenses to, or obtain
insurance or similar cover for, directors.

         The Company's Articles of Incorporation provides for indemnification
of the officers and directors of the Company and eliminates the liability of a
director or officer to the Company or its stockholders for money damages to the
fullest extent permitted by Maryland law.

ITEM 8.  EXHIBITS

         See Exhibit Index appearing at numbered page 4.

ITEM 9.  UNDERTAKINGS

         The undersigned Registrant hereby undertakes:

         (a)(1)  To file, during any period in which offers or sales are being
made, a post-effective amendment to this Registration Statement:

                 (i)    To include any Prospectus required by Section 10(a)(3)
                        of the Securities Act of 1933;

                 (ii)   To reflect in the Prospectus any facts or events
                        arising after the effective date to the Registration
                        Statement (or the most recent post-effective amendment
                        thereof) which, individually or in the aggregate,
                        represent a fundamental change in the information set
                        forth in the Registration Statement;

                 (iii)  To include any material information with respect to the
                        plan of distribution not previously disclosed in the
                        Registration Statement or any material change to such
                        information in the Registration Statement;


         Provided, however, that paragraphs A(1)(1) and A(1)(ii) do not apply
if the information required to be included in a post-effective amendment by
those paragraphs is contained in the periodic reports filed by the Registrant
pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 that are
incorporated by reference in the Registration Statement;

         (2)     That, for the purpose of determining liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to
be a new Registration Statement relating to the securities offered therein, and
the offering of such securities at that time shall be deemed to be the initial
bona fide offering thereof;

         (3)     To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

         (b)     The undersigned Registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act, each filing of
the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of
the Exchange Act (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the Registration Statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (h)     Insofar as indemnification of directors, officers and
controlling persons of the Registrant for liabilities arising under the
Securities Act of 1933 may be permitted, pursuant to the provisions referred to
in Item 6 of this Registration Statement, or otherwise, the Registrant has been
advised that in the opinion of the Securities and Exchange Commission, such
indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the
matter has been settled by controlling precedent, submit to a court of
appropriate jurisdiction the question of whether such indemnification by the
Registrant is against the public policy as expressed in the Act and will be
governed by the final adjudication of such issue.


                                        2
<PAGE>   3
                                   SIGNATURES

         Pursuant to the requirement of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Santa Fe, New Mexico on June 2, 1997.

                                      THORNBURG MORTGAGE ASSET CORPORATION


Date: June 2, 1997                    By  /s/ LARRY A. GOLDSTONE
                                         -----------------------
                                         Larry A. Goldstone
                                         President


                               POWER OF ATTORNEY

         We, the undersigned directors and officers of Thornburg Mortgage Asset
Corporation, do hereby constitute and appoint Larry A. Goldstone, our true and
lawful attorney and agent, to do any and all acts and things in our name and
behalf in our capacities as directors and officers and to execute any and all 
instruments for us and in our names in the capacities indicated below, which
said attorneys and agents, or any one of them, may deem necessary or advisable
to enable said corporation to comply with the Securities Act of 1933, as
amended, and any rules, regulations, and requirements of the Securities and
Exchange Commission, in connection with this Registration Statement, including
specifically, but without limitation, power and authority to sign for us or any
of us in our names and in the capacities indicated below, any and all
amendments (including post-effective amendments) hereof; and we do hereby
ratify and confirm all that the said attorneys and agents, or any of them,
shall do or cause to be done by virtue hereof.

         Pursuant to the requirements of the Securities Act of 1933, as
amended, this Registration Statement has been signed below by the following
persons in the capacities and on the dates indicated.

<TABLE>
<CAPTION>

         Signatures                      Title                           Date Signed
         ----------                      -----                           -----------
<S>                                <C>                                   <C>    
/s/  H. GARRETT THORNBURG, JR.     Chairman of the Board                 June 2, 1997
-------------------------------    
H. Garrett Thornburg, Jr.

/s/  LARRY A. GOLDSTONE            President and Director                June 2, 1997
-----------------------------
Larry A. Goldstone


/s/ RICHARD P. STORY               Chief Financial Officer and           June 2, 1997
-----------------------------        Treasurer (Principal
Richard P. Story                      Accounting Officer)
           
/s/  JOSEPH H. BADAL                      Director                       June 2, 1997
-------------------------------
Joseph H. Badal

/s/  OWEN M. LOPEZ                        Director                       June 2, 1997
-------------------------------
Owen M. Lopez

/s/  STUART C. SHERMAN                    Director                       June 2, 1997
-------------------------------
Stuart C. Sherman
</TABLE>



                                       3
<PAGE>   4
                        EXHIBIT LIST
<TABLE>
<CAPTION>

    Exhibit                                                           Sequentially
    Number        Description                                         Number page
    ------        -----------                                         -----------
    <S>           <C>              
     4.1.1        Amended and Restated 1992 Stock Option and 
                  Incentive Plan (previously filed as Exhibit 10.3
                  to the Company's Form 10-K for the period ending
                  December 31, 1996 (file no. 001-11914) and
                  incorporated herein by reference)

     5.1          Opinion of Jeffers, Wilson, Shaff & Falk, LLP

    23.1          Consent of counsel (included in Exhibit 5.1)

    23.2          Consent of McGladrey & Pullen

</TABLE>



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