Reporting back about applying for a 30-day extension using embassy Covid letter at Samut Prakan Immigration Office at Pak Nam (if I'm not mistaken, I am the first to report about this office. Feel free to comment with any additional questions).
*USA nationality, entered on a Visa-Exempt stamp on 9 March, used 30-day extension to 7 May, then went on amnesty.*
Required:
1. Your passport.
2. 2 (yes, two, explanation below) copies of
* ID page of passport, *signed at bottom*
* Passport page with visa exempt stamp, *signed at bottom*
* Departure card, *signed at bottom*
* Embassy letter (I printed in color, not sure if that's required)
* TM 7 (make sure you have your full, current address on hand to enter on the form correctly)
* A crudely self-drawn "map" of where you live (*signed at bottom)*. *Yes, really*. It seems this was a requirement awhile back before amnesty and it again has made a comeback. Don't worry if you're an awful artist, just include a couple landmarks (BTS, Big C, Tesco, if nearby) and the soi / street you live on, and of course a nice fat square / rectangle for your condo building / house.
* A form acknowledging the overstay penalty. They will provide this. Fill it out first, then have to go outside *again* to copy.
3. ONE passport photo, 4 x 6 cm
4. 1,900 THB
I went just before 1 pm and it was fairly crowded. They make the majority of the crowd wait outside under a few tents with fans, and as your number gets closer, they call you inside to bask in the aircon until your number is officially called.
After receiving my queue number, waiting outside about 30 minutes, and then inside about 30 minutes, I finally brought up the full list of documents as I have listed above *(though with only 1 copy each document, as was reported from CW)*, only to be told to go outside to their copy shack and make additional copies of *the entire stack*, at 3 baht each. In the past for extensions, I've nearly always seen the officer take my stack and immediately make copies of all of them behind the desk, so seems like this office is being overly *thrifty*, to put it nicely...
Result: Given under consideration stamp and "cleared" to return on 29 September *(yes, even after the official amnesty date on 26 September has expired)* and will be given the official extension to 26 October. I was told *(repeatedly)* that my current stamp allows me to stay for sure until 29 September, and I will for sure receive the next stamp to 26 October *(head immigration officer's words, not mine!)*. Again, just relaying *exactly* as I was told.
I also had to go out and make 2 copies of the receipt from paying 1,900 baht and bring it back to them at the very end, before receiving my passport. Again, not sure why this wasn't being done behind the desk, on their own dime.