I stayed at the Le Meridian Bangkok hotel and they made the appointment for me at the BNH hospital. If your staying in BKK before you fly out ask your hotel to make you an appointment somewhere. They can do it. I’ve read there is someplace in BKK that is only 700 baht..I paid 4000 because they sent my rapid test to a lab which took 2 hours for the results.. and it was that price because I wanted a letter from the hospital and not just a picture of a rapid 15 min test stick.
No older than 24 hours before you board your first flight in Bangkok. I did a rapid test and wanted a letter from the lab to take with me..not just a picture of my rapid strip test. I wanted something more definitive. I took the test at 2pm the day before and flew out at 7:10am on ANA.
When I got to Tokyo, United checked my test again.
When I was just in Thailand on the Test &Go and had traveled to Phuket where I had taken my 2nd test, I just kept going places till I got my results which were negative. I was never told to return to the hotel.