Thanks for your answer. I was considering going to Immigration for a residence certificate, because it is a lot cheaper than an affidavit from my embassy. But then I read that it takes 3 weeks in BKK (apparently they send it to you by EMS?). And now this. Better go to the embassy then...

What if you never do 90 day reports because you travel a lot?

No translation needed if the document is in English and has been certified by MOFA at home, embassy at home, and MOFA in BKK.

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.