With Buriram United not in action, Muang Thong took full advantage and went two goals ahead thanks to strikes from Piyapol Bantao and Teerasil Dangda.
Henk Wisman's side were pegged back by Leonardo Ferreira Da Silva's goal in the 66th minute before Jakkraphan Pornsai wrapped things up.
In the clash between Chonburi and Suphanburi, both sides dropped further behind in their bid to catch the top two.
The pair drew 0-0, while Army United suffered a 3-0 defeat against Bangkok Glass.
Goals from Hironori Saruta, Lazarus Kaimbi and Supasek Gagaew secured the three points as Attaphol Buspakom's side moved to within four points of their defeated opponents.
At the bottom of the table, Pattaya United could not take advantage of Chiangrai's defeat as they were beaten at home by Bangkok United.
Bangkok were 2-0 up before Ajoku Obinna pulled a goal back late on scored late on.
Pattaya are now six points adrift of safety, having played a game more than the two sides above them - Chiangrai and Samut Songkhram.
Two second-half goals from Adisorn Daengreuang and Babo Marc Landry were enough to get Songkhram the win against Songkhla United.
John Obregon's goal after 46 minutes gave Ratchaburi victory against TOT, while Yannick Mbengono was the star performer as Chainat beat BEC Tero Sasana 4-2 away from home.
After Seon Power's own goal gave the home side the lead, the Cameroonian striker struck twice before Ratchapol Nawanno added a goal.
Dennis Buschening pulled one back before Mbengono grabbed his hat-trick.
