Europeans have to get a European marriage certificate. This certificate (in about 10 languages, but not in Thai) then has to be certified by their Ministry of Foreign Affairs. Then it needs to be certified by the Thai embassy/consulate in the home country. Finally it needs to be certified by the Thai Ministry of Foreign Affairs. So no need to get a translation of the certificate. I have been told that you only need to go through this process once. For your second renewal a recent certificate, but without all the certifications, should do the trick.
