Getting Fiancee or spousal visas for Vietnam is much harder than from most other countries. 

The consular officers in Ho Chi Minh City apply a higher standard before they accept that a relationship is genuine. 

Like the consulate in China, see
Guangzhou Problems they expect a petitioner to have made multiple trips, to have had a
long engagement, and to be able to communicate well with his fiancee
(English no problem). 

In addition they expect each petitioner to have celebrated a large, formal engagement party and banquet called "Dinh Hon" (but not on the first trip). 

Some of their "official" reasons for denial are:

Photographs
submitted as evidence of the relationship indicate that Petitioner and
Fiancee have spent only four or five days together. 

(This
is their "code" what it really means is "only one trip = no visa".  If
only one trip, it doesn't matter how many photos you give)

It
does not appear that the claimed relationship is continuous and on
going.  For example, Petitioner has not returned to visit Fiancee for
one year. 

Fiancee and-or Petitioner
submitted evidence of only a small, inconsequential engagement ceremony
without any US guest.  This contradicts local social and cultural norms
in which many family members and friends, including those in the US,
are invited to engagement celebrations numbering in the hundreds of
guests for families of even modest means. 

In
contrast to Vietnamese social and cultural norms which mandate a
lengthy and careful period of pre-nuptial arrangements, Petitioner and
Fiancee became engaged before meeting in person. 

The
decision to approve or deny is generally made by the consular officer
before he meets with the Fiancee, before the interview.  This is why
taking the extra effort to make a complete and convincing petition at
the start is essential to your success.  If the officer has decided to
deny, he will ask her detailed questions about the "proposal, the
petitioners home town or the future wedding plans".  Any answer the
Fiancee gives will not be "credible". 

Beneficiary's
chronology of the claimed relationship is not credible.  For example,
Fiancee can not recalled when Petitioner proposed to her. 

Fiancee
is unaware of basic facts regarding Petitioners location and or
hometown (features, characteristics, etc).  For example Fiancee was
unaware of where Petitioner has lived for the past two years. 

Fiancee is unaware of the exact wedding plans, what church, or venue, when the marriage would take place. 

If these issues apply to you, to be successful you MUST remedy them prior to submitting your Petition.  And you MUST
provide the supporting documents to irrefutably prove the remedies have
occurred.  Many petitioners have their multiple trips and engagement
party after the fiancee visa petition has been submitted, then bring
proof of the trips, etc to the Fiancee's consulate interview.  They
leave dumbfounded when finding that their Fiancee who attended the
interview alone, but with all the documents, was not allowed to show
the proof, instead was asked a few questions and left, denied due to
the weak initial petition documentation. 

Submit a stronger petition with more "proof of a genuine relationship", UP FRONT. 
Contrary to official statements, decisions to accept or deny a petition
are often made early, prior to the interview, while the consular
officer is reviewing your petition.  The officer then asks pointed
questions during the interview in order to justify the decision he has
ALREADY made.  Be sure to provide all proof of your genuine relationship
"up front" in the petition. 

Strategy
to successfully petition: Immediately take extra care to ensure that
your "paper trail" is solid, and put at least two trips to meet her
into your plans, sign her up for English lessons if her conversational
English is not good, and celebrate your "Dinh Hon" during one of your
trips. 

Fred Wahl is Bonded by the State of California as an Immigration Consultant,
qualified to coach in the non-legal, technical procedures of immigration form preparation, and document selection. 
Whenever legal advice or legal representation is needed, the service of a qualified
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