So you want your Thai in-laws, relative, or girlfriend to visit the US? The question of how a Thai person can get a visitor’s visa (B2 visa) has often been raised on TFB. Generally speaking, while the paperwork and process itself is relatively simple, getting a visitor’s visa granted can be quite difficult. Namely because the Thai applicant has the burden of showing the US government that he/she is going to return to Thailand. This is done by providing strong evidence of ties to Thailand (ie, family, economic, and social ties). [Student (F) visas and employment-related (B1) visas will not be discussed here.]

After you’re done reading this, go to this page on the US Embassy (Bkk) website:  B2 Instructions   Here you will find the step-by-step instructions on the procedures for applying (it is in PDF format). Basically, the Thai applicant has to first pay a fee of $100 (USD) at one of the designated Thai post offices listed on the website. Then the applicant must make an appointment for an interview via the website or by telephone. See  Interview Scheduling  As a side note, this process differs from the K1 or I130 visas, which does not use phone or website scheduling.  (When appearing for the interview, the applicant need not stand in line--go to the entrance and show the appointment letter.)

Paperwork: The applicant will need to complete forms DS156, which must be completed online and printed out (and she will receive a bar coded cover sheet); and DS157 (which can be printed out and handwritten in English only).  There is also a postal office form used to designate where the applicant wishes to receive her passport--this postal office form must be mailed in a special envelope purchased at the Embassy.  Each applicant (if more than one) must complete his/her own form. When going to the interview, she will need to bring her Thai passport, fee receipt, DS156 & 157, photo (per requisite dimensions, to be glued [not stapled] to the DS156), postal office form (and envelope), and documentation to show "evidence of ties".

"Evidence of Ties"... essentially, the applicant will need to show that: 1) she does not intend to abandon her Thai residence, 2) she intends to enter the US for a specifically limited duration, and 3) she seeks admission for the sole purpose of engaging in activities relating to pleasure (vs. employment, schooling, etc.). Again, the intended stay must have a time limitation and not be indefinite in nature. The applicant must have specific and realistic plans for the entire period of the contemplated visit. Also, the applicant must have made adequate arrangements for defraying the expenses of her trip and return (i.e., she must have sufficient funds to support her stay and prevent work in the US).

The documentation for "evidence of ties" can be various things such as employer letters, business records (if self-employed), bank records, home-ownership records, birth and marriage certificates, house registry, etc. An American relative or friend cannot "sponsor" an applicant or "guarantee" her return, however a letter in support of the applicant with details on length and purpose of stay may be submitted. The American relative can even provide an affidavit of support  (the USCIS's I-134) on behalf of the applicant (a good idea if your in-laws are poor Isaan rice farmers). Here is a section from the website titled: How Can I Help

B2 visas are usually granted for a period of 6 months (must enter within 6 months), but can be granted for a period of up to 10 years--so within the 10 year period, multiple entries can be made.  It is at the POE or port of entry (not at the Embassy), where the immigration official will determine the allowed length of stay (generally 6 months). The '10 year' visa should be requested so the applicant does not have to re-apply for every visit--however it usually is granted for a repeat applicant versus a first-time applicant.  Admission can be denied at the POE, so the applicant should bring all her documentation. 

Each application is determined on a case-by-case basis and there is no one thing or document that can assure the granting of a B2 visa. If the visa is denied, there is no appeals process, but the applicant can re-apply at any time.  For more information, go to:  Embassy visa page  and look under the section on non-immigrant visas. Also post your questions on the TFB under the US immigration folder.