Current clubs:
Northern Region: Chiangrai City3 | Chiangrai Lanna3 | Kamphaengphet1, 3 | Maejo United3 | Nakhon Mae Sot United | Nan3 | Northern Tak United3 | Phitsanulok3 | See Khwae City3 | Uthaithani FC | Uttaradit Saksiam3 | Wat Bot City3
North Eastern Region: Khonkaen Mordindang4 | Mahasarakham4 | Mashare Chaiyaphum4 | Muang Loei United4 | Nakhon Ratchasima United4 | Sakon Nakhon4 | Sisaket | Sisaket United | Surin City4 | Surin Khong Chee Mool4 | Ubon Kruanapat1, 4 | Udon United4 | Yasothon4
Eastern Region: ACDC5 | Asawin Kohkwang United5 | Banbueng2, 5 | Bankhai United5 | Chachoengsao1, 5 | Chanthaburi5 | Marines Eureka5 | Pattaya Dolphins United5 | Pluak Daeng United5 | Royal Thai Fleet5 | Saimit Kabin United5 | Sakaeo1, 5
Western Region: Angthong6 | Assumption United6 | Bang Pa-in Ayutthaya1, 6 | Chainat United | Hua Hin City6 | Kanjanapat6 | PTU6 | Samutsongkhram6 | Saraburi United6 | SGB Kanchanaburi6 | Thawi Watthana Samut Sakhon United6
Southern Region: Jalor City7 | Krabi7 | MHKhon Surat City7 | Nakhon Si United2, 7 | Nara United2, 7 | Patong City7 | Pattani7 | Phatthalung7 | Satun United7 | Songkhla7 | Surat Thani2, 7 | Trang2, 7 | Young Singh Hatyai United
Bangkok Metropolitan Region: Bangkok8 | Chamchuri United2, 8 | Grakcu Sai-Mai United8 | Inter Bangkok2, 8 | KBU2, 8 | NBU8 | Nonthaburi United8 | Prime Bangkok8 | Royal Thai Air Force8 | Royal Thai Army2, 8 | Samut Prakan FC8 | Siam8 | STK Muangnont8 | Thonburi United8
Former clubs: Amnat United1 | Ayutthaya United1 | Customs Ladkrabang United2 | Kalasin1 | Khonkaen1 | Krung Thonburi2 | Lamphun Warrior1, 3 | Muangkan United6 | Nakhon Pathom United | Phayao1 | Phrae United1 | Raj Pracha2, 6 | Ranong United2 | Samutsakhon2 | Singburi Bangrajun1 | Udon Thani1
Dissolved Former clubs: Simork2
Related: Thai League 2 | Thailand Amateur League | Thai FA Cup | Thai League Cup
1Original 2016 clubs in Upper Region
2Original 2016 clubs in Lower Region
3Original 2020-21 clubs in Northern Region
4Original 2020-21 clubs in North Eastern Region
5Original 2020-21 clubs in Eastern Region
6Original 2020-21 clubs in Western Region
7Original 2020-21 clubs in Southern Region
8Original 2020-21 clubs in Bangkok Metropolitan Region
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