Update, my wife and I who are both Canadians successfully got 60 day extensions yesterday for 1900 baht.
Stamp was extended to January 29th from Nov 30th.
Whole process took about an hour with the help of this post and some of the volunteers at the Chiang Mai Immigration double checking the paperwork before we went inside.
Cory Rose Just wanted to confirm if you did this at Promenada or the Immigration near the airport -- I've been seeing conflicting comments, last time we were at Promenada they told us we'd have to go to the one by the airport for this. Is that what you did?