Chonburi's challenge for the Thai League 1 crown showed signs of losing steam as they suffered a shock 1-0 defeat at Nakhon Ratchasima on Sunday night.
The winner was headed home by Jordan Murray in the 19th minute and the Swat Cats successfully warded off a number of late attacks launched by Chonburi to seal three points.
Elsewhere, Lamphun Warriors emerged 2-1 winners over Lampang in a northern derby last night.
In another game, hosts Khon Kaen United and 10-man Police Tero shared the spoils after a goalless stalemate.
Earlier on Saturday night, defending champions Buriram United were assured of the top spot at the end of the first leg when they defeated Port 3-1.
The Thunder Castle will play their last match against Ratchaburi on Friday before the league goes into the mid-season break after the weekend.
Strikes from Theerathon Bunmathan (36 minutes) and Peeradon Chamratsamee (90+2) sandwiched a 76th-minute own goal by Elias Dolah at the PAT Stadium where Elias had earlier scored the home team's only goal shortly before the break.
Buriram coach Masatada Ishii said: "We were the away team and got three points, so I am happy."
Also on Saturday night, Chiang Rai United captured three points with a 3-1 victory over Muang Thong United.
The Kirins coach Mario Gjurovski said: "I am not sure what changes will be made to the team during the break so let's see what happens."
Meanwhile, hosts Sukhothai and Nongbua Pitchaya played out a goalless draw on Saturday night.
