A few days before the appointment they sent me a text message reminder and confirmation.
I self-drove to Phyathai 2 located near the Victory Monument and normally at this time it's a traffic clogged location but with the Bangkok lock-down it was a breeze. I noticed construction sites closed with the Army conspicuously standing guard. I arrived at 1430hrs. There were around 100 or so people getting the vaccine, mostly white guys but also Indians and Asians.
The vaccination center was on the 7th floor and was well signed. There were 5 stations you quickly rotated through, separate spaced waiting areas with chairs. They took your blood pressure, temp, pulse, weight and height.
This round of vaccinations was for those over 60 years of age and/or with certain medical conditions such as diabetes. The web page said something about having proof and having medical records. I was well prepared with 6 months of medical records from Bumrungrad on a PDF file on my phone. Others I noticed had printed medical papers and folders. None of that was needed. You just signed a pre-printed one page form and check a few simple blocks. All I really needed was my passport. There was no address check other than asking me if I lived in Bangkok.
After getting the vaccine the last station is a 30 min observation section. Then you're given an appointment in two weeks for the second shot.
Total time from the parking lot to out the door 1 hour and 1/2. Overall a very pleasant experience and not what I expected. There were no charges, it was all FREE even parking was FREE.
