2018 Thai League 3 Upper Region is the 2nd season of the Thai football league. It is a part of the Thai League 3 and the feeder league for the Thai League 2. A total of 14 teams will compete in the league this season, after Amnat United and Phayao withdrew before the season started.
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
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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).
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Source: Thai League 3