 Three clubs were promoted from the 2017 Thai League 4

Two clubs were promoted to the 2018 Thai League 2

A club was relegated to the 2018 Thai League 4 Northern Region

A club was relegated from the 2017 Thai League 2 





A T3 team could registered five foreign players by at least one player from AFC member countries and at least one player from ASEAN member countries.A team can use four foreign players on the field in each game, including at least one player from the AFC member countries or ASEAN member countries (3+1).Source