1. Closures of all Points of Entry into the Kingdom by air, water, or land
2. The people who can travel to Thailand are as follows:
• An exempted person, as prescribed or permitted pertaining to necessity by the Prime Minister or Chief Official responsible for remedying the emergency situation whereby conditions and timeframes may also be prescribed;
• Carriers of necessary goods, who shall promptly depart after completing their mission;
• Vehicle operators and crew members of vehicles, who need to enter into the Kingdom pursuant to their mission, with a clear scheduled time of departure;
• Persons on diplomatic or consular missions or under International Organizations, or representatives of the government performing their duties in Thailand, or other persons or international agencies, including their families, that the Ministry of Foreign Affairs gives permission pertaining to necessity, shall apply for documents as described in Section 3;
• Non-Thai nationals who have work permits or have been granted permission from government agencies to work in the Kingdom, and who shall also comply with Section 3;
• Thai nationals who shall apply for a certificate of entry into the Kingdom from the Royal Thai Embassy or the Royal Thai Consulate in their country of residence, (or/and – which conjunction is it? If they only have a letter and no certificate, can they enter? Also how is the medical certificate different from the Fit to Fly Health Certificate?) has a medical certificate, and who shall comply with Section 3;
3. Persons granted with an exemption or relaxation must have a Fit to Fly Health Certificate which has been certified or issued no more than 72 hours before travelling;
4. Upon entry into the Kingdom, people must also strictly comply with disease prevention measures prescribed by the Government
https://ddc.moph.go.th/viralpneumonia/eng/ind_traveltoeng.php