Leaders Bangkok United on Saturday night suffered a shock 2-1 defeat at Muang Thong United that could eventually cost them their dream of winning a maiden Thai League 1 title.
Although the Angels remain three points clear at the top, defending champions Buriram United have three games in hand.
Songwut Kraikruan put the Kirins ahead in the 19th minute but Bangkok United striker Richairo Zivkovic produced the equaliser five minutes before half-time.
The hosts came back strong in the second half and got the winning goal in the 76th minute from Felicio Brown.
Bangkok United coach Totchtawan Sripan praised the Kirins, but added: "The international break affected the momentum of the team. We have to move on and concentrate on our remaining matches."
Meanwhile, Uthai Thani settled for a 1-1 draw against Port.
Lonsana Doumbouya gave Port the upper hand in the eighth minute but Uthai Thani struck in the 79th minute through Justin Baas to earn a point from the home game.
Also on Saturday night, Rayong let bottom-placed Nakhon Pathom United off the hook in a 2-2 draw at home.