PSA: If your Thai girlfriend has applied for a tourist visa (u.s. specifically) the consulate has already approved/denied it BEFORE the interview. Found this out the hard way today. We had all the proper documentation and every reason for a tourist visa and NOT a K1 or any other visa. Neither of us wishes to live in the U.S. They didn't look at a single document, passport, or anything else. 3 questions, what's your boyfriend do for work, what do you do for work, and how long did you plan to stay in the u.s.? Denied in under a minute.
SUGGESTION: for those applying for a legitimate tourist visa for their girlfriend. They will be denied the first time, almost 100%...BUT, you can apply again immediately and in the next interview (even though they will likely be expecting to deny it pre-interview date) ask them to reconsider. State you were denied, and you are reapplying because you'd like them to reconsider, and explain why you will not be using the tourist visa to stay in America and not come back, and that you have all the supporting documents and reasons, that show your gf/bf will return to Thailand.
Just food for thought, for those in the same situation. I'm not a lawyer, but a lawyer was the one that said it was denied pre-appointment, and the interview is just a formality.