Can I obtain a multiple-entry permit after entering Thailand on a Non Immigrant O-A visa with single entry?

Just make sure when you leave that you get the exit/re-entry stamp at the airport?

@Hans ******

IF in fact you were sold a single entry Non-Immigrant Type O-A visa (which actually does exist just is very rarely issued) once you get in to the country you will be stamped in for a year (or how ever long your 100K USD covid and 40k/400k out/in-patient health insurance is valid for up to a year)

You could go to the immigration office and buy a re-entry permit (single re-entry 1000baht, and multiple re-entry 3800baht) and that would allow you to exit/re-enter and get stamped in until the original entry stamp you got when you first came in expires during that time.

If they are telling you it is a single entry then you might want to check and see if they are really giving you an OA visa.

@Hans ******

no matter what the "agency" told you, when you get the visa sticker in your passport LOOK at it and see what it says. It will clearly stating whether it's a single or multiple entry under the "No. of Entry"

A Non-OA visa is a one year multiple entry visa. On each entry you are stamped for one year. You can enter and leave as many times as you like on the visa.