Is Chaeng Wattana still open on Saturdays and how does the Non-O Extension of Stay renewal work for marriage?

No, there is still the 30 day under consideration stamp given. That has not changed. I just did mine in September. They did just give a bunch of promotions to immigration agents, so don't expect it to be trouble free, even when you have all the correct documents. For the last three years we had the same immigration agent review our documents, and never a problem. She got a promotion, and the new agent we had found three problems, that weren't actual problems, and instead of mentioning them all at once, she chose to want them corrected one after another. The supervisor that everything goes to when she was done, the one that actually approves everything, threw away all three of the corrections she wanted done, as those documents were already in our packet, and correct. My wife was ready to slap some sense into her.