Can I apply for a 60-day COVID extension for my tourist visa while staying in Bangkok?

You apply for the 60 day covid extension where you stay.

SO if you're staying in Bangkok (and can prove it) you can apply for a covid extension at Chaengwattana Immigration office Counter J <- the counter that people with tourist visas use for extension.

BUT

keep in mind, when you apply for a covid extension (especially in bangkok) you will get a 14 day "under consideration" stamp and then have to go back to that same immigration office to get the "loop closed" <- have the covid extension inked in.

That means if you're not gonna be here in bangkok 2 weeks after you apply for the covid extension, just wait and do it back where you live at your Sri Racha immigration office