The 2021–22 Thai League 2 is the 24th season of the Thai League 2, the second-tier professional league for Thailand's association football clubs, since its establishment in 1997, also known as M-150 Championship due to the sponsorship deal with M-150. A total of 18 teams will compete in the league. The season is scheduled to begin on 14 August 2021 and is scheduled to conclude on 22 May 2022. The 1st transfer window is from 4 May 2021 to 27 July 2021 while the 2nd transfer window is from 8 December 2021 to 4 January 2022.