I need to renew my British passport, and will be returning to the UK for a month soon, so I'm considering doing that there. I have an active marriage visa and would be returning to Thailand on that visa (with a re-entry permit). My only concern is the Passport Office in the UK will cancel the old passport and cut the corner off it. And the visa will not be transfered to my new passport.
So my question is - is it possible to enter Thailand with a valid visa in a canceled passport?
TLDR : Answer Summary
You can enter Thailand with a valid visa in a canceled passport. Make sure to carry both your old canceled passport (with the valid visa) and your new passport when you re-enter Thailand. Upon arrival, show both passports to immigration. After entering, visit your nearest Thai immigration office to transfer your visa to the new passport.