The 2018 Thai League 3 (known as the Omsin League Pro for sponsorship reasons) football season will be the second season of Thai League 3. 31 clubs will be divided into 2 groups (regions).
Promoted to the 2018 Thai League 2
Promoted from the 2017 Thai League 4
Relegated to the 2018 Thai League 4 Northern Region
Relegated to the 2018 Thai League 4 Western Region
Relegated from the 2017 Thai League 2
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This round was featured by Ayutthaya United, the second place of 2018 Thai League 3 Upper Region and Nara United, the second place of 2018 Thai League 3 Lower Region. Winners of third place play-off would promoted to 2019 Thai League 2.
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Ayutthaya United won 2âÂÂ1 on aggregate.
This round was featured by JL Chiangmai United, the first place of 2018 Thai League 3 Upper Region and MOF Customs United, the first place of 2018 Thai League 3 Lower Region. Both winners and runners-up would promoted to 2019 Thai League 2 automatically.
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JL Chiangmai United won 2âÂÂ0 on aggregate.