| Season: | 2009 |
| Winners: | Muangthong United |
| League Topscorer: |  Anon Sangsanoi(BEC Tero Sasana) (18) |
| Highest Scoring: | Chonburi 2-5 Muangthong United Nakhon Pathom 2-5 Bangkok Glass (7) |
| Highest Attendance: | Muangthong United 1–1 Chonburi (16,608) (4 October 2009) |
| Nextseason: | 2010 |
The Thai Premier League 2009 was the thirteenth season of the Premier League since its establishment in 1996. A total of 16 teams competed in the league, with PEA FC as the defending champions.
Muang Thong United took the league championship with two games remaining, the first ever team to win the championship in their debut appearance in the top flight.
Nakhon Pathom, Sriracha and Chula United were relegated to the 1st Division.
1 Pattaya United and Bangkok Glass took the places of Coke Bangpra and Krung Thai Bank after purchasing the clubs. Coke Bangpra and Krung Thai Bank therefore withdrew from the league allowing Pattaya and Bangkok Glass to take position in the top flight.
2 Changed name from Bangkok University
3 Changed name from Thailand Tobacco Monopoly
4 Changed name from Port Authority of Thailand.
5 Changed name from Royal Thai Navy
| Team | Outgoing manager | Manner of departure | Replaced by | Date of appointment | Position in table | |
|---|---|---|---|---|---|---|
| Chonburi | Jadet Meelarp | End of Contract | Kiatisuk Senamuang | January 2009 | Pre season | |
| Chula United | Kiatisuk Senamuang | End of Contract | Carlos Ferreira | January 2009 | Pre season | |
| TTM Samut Sakhon | Prajuk Viengsong | End of Contract | Attaphol Puspakom | January 2009 | Pre season | |
| Muang Thong United | Surasak Tansurat | Taking charge of club's junior sides [4] | Attaphol Puspakom | April 2009 | 4th | |
| TTM Samut Sakhon | Attaphol Puspakom | Moved to Muang Thong United | Kij Meesrisuk | April 2009 | 11th | |
| PEA FC | Prapol Pongpanich | Resigned due to fan pressure | Thongsuk Sampahungsith | May 2009 | 12th | |
| Bangkok Glass FC | Hans R. Emser | Was acting coach and is now Technical Director Youth Football Academy Bangkok Glass FC[5] | Surachai Jaturapattarapong | June 2009 | 1st | |
| Pattaya United | Pansak Ketwattha | Resigned | Wisoon Wichaya | June 2009 | 13th | |
| BEC Tero Sasana | Christophe Larrouilh | Resigned to become the team's Technical Director [6] | Tawan Sripan | June 2009 | 5th | |
| Pattaya United | Wisoon Wichaya | Short term replacement | Jadet Meelarp | June 2009 | 13th | |
| Chula United | Carlos Ferreira | Resigned | Pichai Pituwong | August 2009 | 16th | |
| TTM Samut Sakhon | Kij Meesrisuk | Release | Prajuk Viengsong | August 2009 | 12th | |
| Nakhon Pathom FC | Chatchai Paholpat | Release | Piyapong Piew-on | September 2009 | 14th |
Last updated October 18, 2009
| Scorer | Goals [8] | Club |
|---|---|---|
| Anon Sangsanoi | 18 | BEC Tero Sasana |
 Kone Mohamed | 14 | Chonburi |
| Nantawat Tansopa | 11 | Bangkok Glass |
 Ajayi Samuel | 10 | Bangkok Glass |
| Dango Siaka | Muang Thong United | |
| Pipat Thonkanya | Thai Port | |
| Arthit Sunthornpit | 9 | Chonburi |
| Sarayoot Chaikamdee | Osotsapa M-150 | |
| Sompong Soleb | Chula United | |
| Soumahoro Yaya | Muang Thong United | |
| Suriya Domtaisong | Muang Thong United (2 goals) PEA (7 goals) | |
| Michael Byrne | 8 | Nakhon Pathom (4 goals) Chonburi (4 goals) |
| Suttinan Nontee | Rajnavy Rayong | |
 Anderson | 7 | Chonburi (3 goals) Pattaya United (4 goals) |
 Bekombo Ekollo | TTM Samut Sakhon | |
| Chakrit Buathong | BEC Tero Sasana | |
| Chatprapob Usaprom | TTM Samut Sakhon | |
| Chatree Chimtalay | Bangkok Glass | |
| Jirawat Makarom | Thai Port | |
 Raúl González Gastón | Sriracha | |
| Teerasil Dangda | Muang Thong United |
| Key | ||
|---|---|---|
| 4 | Player scored four goals | |
| 5 | Player scored five goals | |
| Player | Nationality | For | Against | Result | Date | |
|---|---|---|---|---|---|---|
| Chula United | 3–1 | |||||
| BEC Tero Sasana | 4–0 | |||||
| Bangkok Glass | 5–2 |