You are still a foreigner and need to use the channel for foreign passports only. When you are married to a Thai passport holder, sometimes they will allow you both to go trought the Thai passport channel together.
I did an extension yesterday in Chiang Mai and it was required. I saw a few ppl who did not get it from their landlord and the immigration officer called them in to come fix it and pay a 1.600 thb fine. They're not joking around.