17 May 2020 : In regards to the continuity of the prevention of the spread of COVID19, on 16 May 2020 the Civil Aviation Authority of Thailand (CAAT) announced the "Extension of temporarily ban on all international flights to Thailand until 30 June 2020". This means that although domestically Thailand is opening slowly again and domestic airports are opening again that you still can not fly international to Thailand until 30 June 2020. Mind you there are at the moment flights going to/from Bangkok but this are flights for foreigners leaving Thailand or for Thais coming back to Thailand.
So theoretically from 1 July 2020 you could fly again internationally to Thailand. But be aware that it could be that the Thai government changes its mind again. And be aware that it could be that the Thai government will have extra regulations for foreigners to enter Thailand. Also be aware that it could be that your home country will have extra regulations on people returning home from some countries.
Personally I would not yet book any flights or holidays for this year (2020) and I would just wait what will happen in following next 2 or 3 months.
Photo below is a screenshot of FlightRadar24 with a KLM flight from Amsterdam to Bangkok, an Etihad Cargo flight from Saigon to Abu Dahbi, an Air Asia airplane on Don Muang Airport and a K-Mile flight from Bangkok to Hanoi. But normally this screen shot would see yellow from all the flights.
Disclaimer : All information is created in good faith and is an expression of fair comment.