I've booked with Dam. There seem to be some good reviews and I think I read they do work for the airport too. Supposed to be test/result emailed the same day.
I've been to my GP who refused to sign/issue certificates, another 2 local GPs who don't want to know and suggested a private clinic (who want £600), 🙄 dispair...
Are you doing the quarantine in a hotel, and if so did you book it through the Thai Embassy website? I'm looking at booking but when you follow the link for the Covid 'package' it's like a normal online hotel booking system mentioning free breakfast include and free cancellation... I was expecting it to give a price for 15 nights, 3 meals a day and transport from the airport?