I hope it's ok to use this thread to share my experience at BKK immigration (MTT counter K).
In and out in 1h. Overall, it was smooth. But it was also my first covid extension with the new passport.
I received the documents from the 'screener', then proceeded to see an immigration officer. There were 30-40 people in the room. Most were waiting for their passport. Only 7 were ahead of me in the queue.
No words were spoken by the immigration officer except 'photo' (meaning "take your mask off, i take a photo of you") and 'wait there' (to receive my passport with the 60 days covid extension). Another 30min went by and I received my passport back with 60 days added on top of the previous expiry date.
No letter from embassy needed, no outbound flight ticket, no tm30.
But while I was filling out the documents, I heard the screener rejecting one guy. He couldn't even get the documents or get into the queue. He was sent away. Some were told by the SCREENER "you only get 7 days", "you only get 15 days", another one "you show flight ticket, why can you not leave thailand, when will you go, ..., you show proof of flight ticket...". I can't say anything about their visa status, # of previous extension and so on, though.
The grumpy, old immigration officer shouted at a farang woman because apparently she had an education visa before but couldn't speak more than 3-4 words of Thai. She asked her several questions why her Thai was basically non-existent but in the end she received 60 days. Other were also told 'this is your last time' when they picked up their passport with the 60 days in it. The usual fearmongering...