I went back to the US, December 31 2021. I had a test PCR test done, with all that frustration. No body checked my paper work. I had to fill out a form saying where I would be staying, nobody asked me for the form.
I think the US only requires the ATK test but maybe the Airline require PCR, I am not sure. You will want to check what the airline requires, and for good measure check what the departing and transit airports require
I arrived Phuket February (last month). Agent handled the volunteer visa and converting from volunteer to covid extension in Pattaya. I personally go the second extension from Phuket immigration.