Can a 90-day single entry Non-O visa be cancelled upon leaving Thailand, and is it possible to convert it into a multi-entry visa?

@John ******

a "365-days multi entry Non-Imm-O retirement visa" can only be obtained in the home country where the applicant holds a residence. It cannot be applied for in another country and NOT inside Thailand. . . . . . . . . . The "90-days single entry Non-Imm-O retirement visa" you entered with, cannot be extended, it is already invalid for another use. . . . You can only alter your 90-days stay permit into a "1-year extension of stay permit" by fulfilling the requirements (a minimum of 800,000.-THB in a Thai bank account or proof of monthly income of minimum 65.000.- THB). Once issued, you can buy a multi entry permit for this 1-year stay permit, which will enable you to do unlimited exits and re-entries, as it is leaving your stay permit active. If you choose not to change from the 90 days stay permit to the one-year extension, you will have to LEAVE Thailand before the 90 days are over!

If say you got stamped in until Nov 30 and left with a re-entry permit your next stamp would still only allow you to stay until Nov30

So you are a 90 day non-o visa, if you leave and return in those 90 days WITH a reentry permit you visa remains intact.

If you do a 1 yr extension of stay based on your non-o (in country) you would then purchase a multi reentry permit and you are good to come and go as you like for the duration of the extension.

However it only makes sense if you will leave 4 times or more as has been said.

NOW if you want a multi entry visa (from an embassy outside of Thailand) that requires you to leave every 90 days for the duration of the visa, you just leave and apply at the Embassy without a reentry permit which voids your current visa.

I hope that makes sense as your question is a little on the vague side.

Yes you can go to your immigration office fill out a page of paperwork and sorted in 30 minutes as I did last year

Your visa is already cancelled, it was "used" when you entered the country and cannot be used again.

You cannot convert a visa to multiple entry if it's single entry. But you can purchase a re-entry permit which means the stamp you have in your passport from when you entered Thailand will not be cancelled by leaving. This does not grant you any additional time though, as when you return you will return based on the same stamp that you received previously and purchased the re-entry permit for.