What are the current costs and requirements for COVID extension visas in Thailand?

1900 ... yes available

Up until March 30th you can buy this extension.

You’ll need this stuff. Not all offices have the same requirements so it may be slightly different depending on which of the 70+ offices you use.

A copy of your passport data page,

A passport photo,

Proof of filing a TM30,

A copy of your departure card (TM6)

A copy of your latest entry stamp,

A filled out TM7 (application form for extensions),

A filled out STM2 (acknowledgement that you understand the rules for overstaying)

A filled out “I don’t want to leave because of Covid form” - I have no idea if it has an official name or number.

And 1,900 baht.

The forms are available at your local office. Most have places on site or nearby that can do the copies and photos.