This is the message from the hotel I booked:

After obtaining a confirmation letter – “SUBMIT LATER”
Please send us the following documents:
Vaccination certificate
Flight details
Negative Covid-19 test result (issued no more than 72 hours prior to flight departure)
A Medical insurance document covering all expenditures of medical treatment, including COVID-19 with an amount of at least USD 50,000 (for non-Thai nationality)

Still waiting for the confirmation letter (3 days and counting).