What is the process for obtaining a COVID extension at Chaengwattana, and is TM 30 required?

And you're on a tourist visa entry stamp? <- meaning you bought a tourist visa from a thai consulate before you came here and were stamped in for 60 days when you arrived?

I ask that because if you didn't get a tourist visa before you came here you don't go to Chaengwattana for your extensions in bangkok.

Whether they ask for a TM30 or not depends on if you have any extension from another immigration office (out of province) as they will want you to prove you're staying in Bangkok to apply there.

Also at this time both immigration offices in Bangkok went back to issuing under consideration stamps for covid extensions and you have to go back to that office to get the "loop closed" and get the extension inked in.