Where can I get my Thai Marriage Certificate translated and notarized in Thailand for use in the US?

In kantharalak Sisaket I got mine done by the same person

She is independent and did all my translations for my Thai wife for America. Very nice

Great service

Ministry Of Foreign Affairs Legalized my Marriage Certificate and then this per then US Embassy Web Site. Used for IRS and VA with no problems

Authentication or Legalization of Royal Thai Government Officials’ Signatures

Authentications certify the official seal, signature and/ or authority of foreign officials who perform an official act with regard to a document that is to be used in the United States. The U.S. Embassy may authenticate documents that bear the seal of the Ministry of Foreign Affairs provided their signature is on file with this office. A Consular Authentication does not attest to the authenticity of the contents of a document but merely to the seal and signature of the issuikng Thai government official.

I used British Law on 3rd road near Pattaya City Hospital. I believe the fee was 500฿ but that was 5 years ago.

Most international law firms have notary / translation services?

You could try the ministry of foreign affairs, the same ones that verify and stamp a Thai translation from English as being accurate. They should be able to do the reverse, as it's all the same languages.

Ministry of foreign affairs

I used express translation and they took care everything translating and ministry.

Just use google maps "express translations bangkok"

Embassy should have a list of or link for notarized translaters