2020–21 Thai League 3

The 2020–21 Thai League 3 is the fourth season of the Thai League 3, the third-tier professional league for association football clubs in Thailand, since its establishment in 2017, also known as Omsin League Regional Championship due to the sponsorship deal with Government Savings Bank (Omsin Bank). Due to the COVID-19 pandemic in Thailand, the season must be postponed to start in late 2020 and end in early 2021. In addition, the Thai League 4 had combined with the Thai League 3 and compete as Thai League 3 since this season and there is no relegation in this season. A total of 72 teams would be divided into 6 regions including 11 teams in the Northern region, 11 teams in the Northeastern region, 12 teams in the Eastern region, 12 teams in the Western region, 12 teams in the Southern region, and 14 teams in the Bangkok metropolitan region.