Bottom line, travel departing HK to Thailand will essentially be ground to a halt. The different Ministries in Thailand aren't talking to each other, going back over a week. Add on the requirement for a negative test result which apparently can't be performed by private clinics at this time.
It would seem that if you really wanted to visit TH, the easiest solution would be to travel on a non-BNO, non-HKSAR passport and transit through Singapore/Malaysia/Vietnam, as Thailand's illogical requirements only apply for travel departing HK rather than anyone who's been here recently.