If never been married you need to show the Ministry of Foreign Affairs a statutory statement of non-attachment notarized by your embassy in Bangkok. Your Embassy may require proof of evidence to this fact.
A statutory statement required by the Thai authorities will cost 1,000 Thai Baht each (US$25). Your embassy will normally charge a fee for notarizing it and the Thai Ministry of Foreign Affairs makes a nominal charge for registering it and issuing a certificate to enable you to legally marry anywhere in Thailand. A further fee will be required to have the document officially translated into Thai.
Special attention should be made about pre marriage planning. Assets of the foreigner should be protected. A prenuptial agreement prepared by our licensed lawyer is highly recommended. Prenuptial Agreements should be prepared in both the Thai and English languages. If, for example, the foreigner is a US Citizen with assets in USA and Thailand, the prenuptial agreement should be prepared in such a manner that it is recognized and legally binding in both USA and Thailand. Prenuptial Agreements are less likely to be contested when prepared and signed well in advance of the marriage date.