When I went to Jomtien to extend my non-O visa from "reason of marriage" to "reason of retirement", the immigration officer asked to see marriage certificate, wife's ID and wife's house registration. Was told this is a one-time requirement when changing from marriage to retirement. Might also apply to those extending a non-O visa previously for reason of marriage to any other reason. Had I not been able to produce the required marriage documentation, the immigration officer would not have granted the extension for reason of retirement. Might not matter in your case if you're not trying to extend your non-0 visa, but you might want to double check just in case. Hopefully this will also help anyone else who might otherwise be caught unaware.