Currently, hotels which are already offering quarantine services (ASQ) are most likely to offer the one-night Test & Go scheme.
Some downtown hotels like the Westin do not offer 24/7 availability of PCR tests, which means if you arrive too late on day one you will have to wait until the next morning to do the test and stay another night until you get the test result.
The two airport ASQ hotels, Novotel and the Siam Mandarina Hotel, both offer 24/7 testing with the latter promising that if you check in before 5 am you get the test result by 1 pm.
The Novotel Bangkok Suvarnabhumi Airport Hotel promises the test result within 6 hours even if arriving after midnight.
Some hotels accept bookings through Agoda or booking.com which means you can often cancel free of charge until a day or two before check-in date.
Other hotels require 100% payment of hotel and tests up at time of booking with cancellation only possible in case of a positive pre-departure Covid test.