This was my experience today (18 January 2022). I am staying in Hua Hin so I went to the satellite immigration office in BluPort Mall. I was met by the immigration 'screener' who asked what I wanted to do. When I told him I wanted to apply for a 60-day visa extension based on COVID-19, he told me I would have to go to the main immigration office 8km outside of town.
I had carefully prepared my documents with tips from this forum. I was under the impression that consulate letters for 'confirmation and request for temporary stay' were no longer needed. But that turned out NOT to be true in my case -- even if ticking the second box on the affidavit. Three immigration officers were involved, and all were in agreement.
This is what I had prepared in my application packet (listed in order preferred by my processing io):
Passport
TM7 - application for extension
- with 1 Passport photo
Copy of passport pages
- ID page
- visa on arrival page
- first and only visa extension page
- TM6
Letter for proof of residence (from Juristic office of the condominium where I am staying) *
COVID-19 Affidavit form (with second box ticked)
Proof of insurance **
Proof of vaccination **
* I did not initially have this document in my application packet, but I did have it with me in case. The io immediately asked for it.
** These documents were taken out of my application packet and handed back to me.
I did not have a letter from my consulate, and they would not move forward without it. Once I was able to give immigration the consulate letter, they approved and issued a 60-day visa extension in minutes with no other questions - after collecting BHT1900 of course.
Side note: I also found out from this experience that the letter must be from the embassy of the country of your nationality. A letter from the embassy of your country of residence (if different from your nationality) is not accepted.