The 2020–21 Thai League 3 Eastern region is a region in the regional stage of the 2020–21 Thai League 3. Due to the COVID-19 pandemic, 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 12 teams located in Eastern of Thailand will compete in the league of the Eastern region.