I used Agoda and the Agoda confirmation was accepted by Thai Pass, back in November.
I deliberately selected a hotel with good customer reviews for ASQ. They were very prompt and comprehensive with their answers to e-mails. (Centre Point Pratumnak)
1 Use this link: https://www.agoda.com/quarantineth
If the link ever stops working google something like "agoda ASQ hotels Thailand" and look for a suitable ASQ hotel link.
2 Make sure your room offer explicitly states that it includes the RT-PCR test, transport from the hotel and the 3 meals per day.
3 Consider cancellation terms. I think mine allowed cancellation up to the day before arrival, therefore had my original flight not departed, I could still have cancelled it.
This was all far easier than in 2020.