For Thai citizens wishing to travel to the United States for the holidays, you will need to obtain a US Tourist Visa. It is usually valid for 6 months and its purpose is for travel for tourism, short holiday in the US. Immigration officers are mandated to assume that everyone applying for the tourist visa is planning on staying in the US permanently.
So, it is best to gather much documents to prove your strong ties in Thailand in a form of stable employment, business, assets as an added advantage and finances to show you have enough funds to support your planned US trip. If you have an American boyfriend or girlfriend, it is not advised to apply for a tourist visa, chances of being granted one is very low. It is highly advised to apply for a K1 Visa instead, if you have plans somehow, to get married in the US.
Lately, it has become a bit difficult for Thai nationals to apply for a US Tourist Visa. Applicant of this type of visa will not be easily granted a visa unless they can convince the immigration officials that they will come back to Thailand after their visit to the US. Documents required can never be predicted, so it is best to prepare in advance important paperwork relating to your trip. The above documents mentioned would serve as your guide that would positively show them that you will be coming back to Thailand after your given duration of stay in the US.
The decision on whether to approve or deny your application lies solely on the visa officer conducting your interview. And the DS form completely filled out online and submitted is an important factor. There is no specific formula on making your application successful, if the visa officer believes you then your visa will be granted. If he or she thinks that you are lying or hiding something, he or she can automatically deny your application. It is best to consult with immigration specialists for a hassle free application.