The Thai government has outlined the exact rules and step by step instructions on how to get entry into the country. Anybody entering the country needs to get permission first in the form of a Certificate of entry from a Thai embassy or consulate in your country.
It is quite a process and involves overpriced flight tickets and a 14-day quarantine which you need to pay yourself and starts at about 34,000 THB up to 140,000 THB for the room, food, medical staff, and tests. But might be worth it for people who have families in Thailand and haven’t seen them in months as long as you can afford several thousand USD/EUR in will cost you.
It does seem that normal “no quarantine” tourist arrivals are a far way out with even the “travel bubble” plans the government had has been postponed indefinitely.