Can I activate my non-immigrant OA visa while in Thailand?

Nope, you need to leave and re-enter to activate your Non Imm OA visa

No you’ll have to exit and re enter

@Hans ******

your multi entry Non-Imm-O/A visa is valid for use for an unlimited number of entries within the one year visa validity period. . . . . . .

you will need to activate your O/A visa by doing a "border bounce" – exit Thailand at a land border or by air, turn around and re-enter

Print out the E-visa document.

And have your health insurance policy and the F.I.C. document your insurer signed, ready to show to the Thai immigration officer at the border.

Upon entry into Thailand, you will get stamped in EITHER for 365 days OR at least for the remainder of the period your health insurance is valid (if it's less than one year at this point!)

Make sure you do get your accommodation TM30 registered, and don’t forget your 90-days reports

Go out, and in with the OA

need to leave and reenter. dont know if the fact that visa was issued while you are in TH can be a problem. Per regulation, Embassy cannot issue visa to applicant residing in TH

What part of Thailand are you staying?

You've got to leave and return....

You can only activate your visa when entering Thailand. You cannot activate it from within the country. Whether you want to do a border bounce or not is irrelevant, it's the only way to activate your visa.