First, you must determine whether you or your fiancée are eligible. The requirements are fairly easy, but it pays to make sure you qualify before you go about getting your documentation in order and continuing with the process.
This is what is required to apply:
-You must be over 17
-You must be "mentally sound"
-Unrelated to your fiancee
-Not already married
There are a number of documents that need to be in order before you marry your Thai bride. These include:
-A certification document from your consulate, in both English and Thai.
-Proof of what you do for a living and how much money you make.
-Details of you and your fiancée's previous marriages (if any) and details of any child support or alimony payments.
-Contact details for two referees to vouch for you. These people must live in the same area.
Americans need to go through a slightly more arduous process to marry Thai women than do British or other Westerners. If you are American, you are going to need to get an affidavit from the US consulate that confirms you're following the eligibility requirements mentioned above. As of June 2010, this affidavit costs $55, and requires your US passport along with the same documents mentioned above. Translation costs are not included in the $55 figure.