If you are in Thailand then can ask for consular assistance at the US Embassy in Bangkok. If you are looking for a US visa then you will need to speak to an attorney in Thailand about that. If you are looking for a letter from the Embassy to register your Thai marriage and need a freedom to marry letter or letter of affirmation then see the linked website for more details.
US Embassy in Bangkok
|Address:||95 Wireless Road|
|Office Hours:||Monday through Friday from 7:30 a.m. – 11:00 a.m. and 1:00 p.m. – 2:00 p.m.|
US Consulate in Chang Mai
|Address:||387 Witchayanond Road, Chiang Mai 50300, Thailand|