The 2021–22 Thai League 1 is the 25th season of the Thai League 1, the top Thai professional league for association football clubs, since its establishment in 1996, also known as Hilux Revo Thai League due to the sponsorship deal with Toyota Motor Thailand. A total of 16 teams will compete in the league. The season began on 31 July 2021 and is scheduled to conclude in May 2022. The 1st transfer window is from 4 May to 27 July 2021 while the 2nd transfer window is from 8 December 2021 to 4 January 2022.