I have a urge to go back to Canada for a few months. I am thinking of buying a sailboat when I return and sailing the pacific coast for the summer. I will want to return to Thailand late sept or october. My problem is my retirement visa extension come up in august. August is the best cruising month to go north to many great cruising areas so I would like to be there. Is it possible to go to a Thai consulate in Canada and get the extension of stay done there, or must the extension be done in Thailand?

I know I could get a new visa and go through the whole process a again but wish to stay away from that if possible.

Extension of stay must be done in Thailand at the office serving the area you live.

Starting over is no big deal if you do it in Thailand. Just arrive with non immigrant O visa or convert after arrival and extend with proof of financials. Converting visa exempt or tourist visa costs 2k but might require trip to Bangkok as not all offices do this.