Defending Thai Premier League champions and current leaders Buriram met third-placed Muang Thong at the SCG Stadium on Wednesday, with just four points separating the teams before kick-off.
There was little to choose between them early on, but Venezuelan centre-back Andres Tunez found the breakthrough for the visitors in the 34th minute.
Buriram's hopes of holding out for the win were dealt a blow shortly before the hour mark when Theeraton Bunmathan was shown a red card, but they did enough to see the game out, as Muang Thong fell seven points off the pace.
Second-placed Chonburi returned to winning ways after their 1-1 draw with Singhtarua on Sunday, recording a comfortable 3-1 win at relegation-threatened Air Force Central.
Thiago Cunha's brace put the visitors two goals ahead and although Bang Seung-hwan pulled a goal back in the 53rd minute, Andre Araujo wrapped up the three points in the closing stages.
BEC Tero Sasana missed the chance to leapfrog Muang Thong into third as they slipped to a shock 2-1 loss at TOT - who eased their relegation fears.
Meanwhile, Chainat climbed out of the drop zone after coming from two goals down to defeat Bangkok Glass 3-2 at the Khao Plong Stadium.
Police United were sent into the bottom five after losing 2-1 at home to Ratchaburi.
Sergio Suarez had put the hosts ahead despite Saranyu Intaraat being sent off just after the hour mark, but a brace from the league's top scorer Heberty led the visitors to three points.
In other games on Wednesday, Samut Songkhram remained rooted to the bottom of the table after losing 1-0 at home to Sisaket, while fellow strugglers Songkhla United and PTT Rayong both failed to win - the former losing 2-1 at Singhtarua while Rayong drew 2-2 at Bangkok United.
Suphanburi beat Army United 4-0 to climb to sixth.
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