The 15 clubs advance to the Champion league round.

[1][2] Red Zone : 2018 Thai League 4 Bangkok Metropolitan Region Yellow Zone : 2018 Thai League 4 Eastern Region Pink Zone: 2018 Thai League 4 Western Region Green Zone: 2018 Thai League 4 Northern Region Orange Zone: 2018 Thai League 4 North Eastern Region Blue Zone: 2018 Thai League 4 Southern Region 3rd place from each zone of 2018 Thai League 4 have signed to qualifying in this round.

Preliminary round 1 will be started after finish all matches of all zone by FA Thailand.

[3] The qualifying round will be played in regions featuring clubs from the 2018 Thai League 4 Northern Region, 2018 Thai League 4 North Eastern Region and 2018 Thai League 4 Eastern Region The qualifying round will be played in regions featuring clubs from the 2018 Thai League 4 Western Region, 2018 Thai League 4 Bangkok Metropolitan Region and 2018 Thai League 4 Southern Region Runner-up and 3rd place from each zone of 2018 Thai League 4 and winners from Preliminary round 1 have signed to qualifying in this round.

Winner of Third place play-off round was promoted to 2019 Thai League 3.