- just go to information desk, and they will call someone inside Immigration to come out and sort things out. It's not a big deal, happens all the time. Next time, always check if yer admitted stamps r correct before walking out :)
To register yer marriage at local district office and to get 1 yr extension u will still need to get yer marriage cert notarized by the Embassy and then translated, then both must be stamped by Thai Ministry of Foreign Affairs. Same must be done for data page of yer passport and a Embassy affidavit that states that you guys are married. Then all is taken to local Amphur to be registered. After that and with lots more paperwork, u can apply for the 1 yr Extension.
If Immigration stamped u incorrectly, after ASQ, go back to airport and to the Information Desk and tell them yer problem. They will call someone from inside Immigration to help you. Easy to fix, it just costs u time.