Hey, I wanted to share this with everyone, maybe I missed it, but when I got my extension in Bangkok they did not ask for this.

In Chiang Mai they want 2 photo copies (there's a copy place in the gas station across the street from the immigrant office). One of your T-6 departure card stapled opposite side of your entry stamp, and another copy of your passport photo and opposite page. They want both pages signed AND they also want your phone number hand written below your signature on the second page of your TM.7.

This group has been very helpful so I hope this helps some people. Cheers!