I'm coming up for renewal of the retirement extension next month and it is the first year I can't use an embassy affidavit. So I headed for the Bangkok Bank office at Soi 7. I figured things are as likely to get more restrictive in town than less.
They knew exactly what I was asking for. No surprise, you need your passport and bank book. It took about 30 minutes and 700 baht. I got a letter showing dates, USD received, and baht credited. They attached the computerized transaction records for each deposit.
I should note I have a direct deposit account for my government annuity.