The National Championship was the next stage from the regional stage of 2020–21 Thai League 3. The winners and runners-ups of each region would qualified to this round to finding three clubs promoting to the 2021–22 Thai League 2.
The National Championship was the next stage from the regional stage of 2020–21 Thai League 3. The winners and runners-ups of each region would qualified to this round to finding three clubs promoting to the 2021–22 Thai League 2. (en)