K1 Visa documents are what you will need. The following documents is what you would need for the K1 visa application which is a US fiancée visa for America. You will note that this is only a brief list of documents and you will need to speak to an immigration lawyer about the full and detailed list of documents. This is only a brief overview of the US fiancée visa documents which will be needed. The K1 Visa documents are explained as follows.
K1 Visa Documents
1. Your Thai fiancée is going to need a valid passport with a long expiration date being at least 6 months beyond her stay in the US. It will create additional problems should the passport expire when she only arrives in the US and the visa would need to be transferred.
2. She will need to recent US visa photos. There are photo requirements for the US visa application.
3. You will need to have the Form DS-160 confirmation page and code which you should have as you get closer to the interview phase of the application.
4. There should also be the interview schedule letter which you will get before the interview once the process is complete.
5. There should be an approved Form I-129F which you should also have at the point of the US visa interview.
6. She should have a copy of the Thai criminal record check which she should have by then.
7. There should also be a divorce or death certificate in the case of a previous marriage. Both of you should have these when the interview comes.
8. You evidence of a valid relationship such as phone records, emails, letters and photos should also have been compiled when you started the process. Your immigration lawyer in Thailand would have copies of these should it be required during the interview process.
9. Her medical examination documents would also have been needed at the start of the process. These includes checking for vaccinations as well as a check of communicable diseases.
10. Finally much like everything else, proof of payments of all the fees.
The costs will mainly be covered as part of the legal fees so that there is a central system to access all the documents in the event that it is needed at the Embassy interview. These include but not limited to the petition fee for the Form I-129F as well as the Form DS-160 submission fee and the medical examination fees. There is also the costs which would be related to the filing of all your documentation and translation from the Thai language.
Note that you should only arrange your travel plans when you have the visa in her passport. Anything else would become an issue with additional costs. The K1 visa does not allow your Thai fiancée to work in the United States however you can start the process once married in the US to an adjustment of status. She would need to file an Employment Authorization Document (EAD). Once that is approved she can then apply for a Social Security Number (SSN). K1 Visa documents are explained above and if you dont understand then speak to an immigration lawyer about this.