Substitute Jay Simpson scored the winner for the Thunder Castle after 78 minutes in the charity match.
Muang Thong, who finished second behind Buriram in the Thai Premier League last season, are still looking for their first-ever win against the Thunder Castle since the league champions were established in 2010.
They are the only two sides to have won the TPL since Muang Thong were promoted to the top flight in 2009.
Muang Thong also lost to Buriram in last year's King's Trophy match.
The game normally pits the TPL champions against the FA Cup winners. But Buriram swept all three major domestic trophies last season so Muang Thong were assigned to play.
It was a lively match with Muang Thong featuring former England striker Jay Bothroyd and Thailand forward Teerasil Dangda who both had chances early on.
Marshalled by midfielder and captain Suchao Nutnum, Buriram were the better side in the first half with Suchao himself squadering a couple of good chances.
Suchao won a penalty after 38 minutes but his shot was denied by goalkeeper Wissanusak Kaewruang.
A few minutes later, Carmelo Gonzalez did send the ball into Muang Thong's net but his attempt was ruled offside. Gonzalez had another clear chance early in the second half but his shot sailed over the bar.
English forward Simpson came on for Leandro Torres and almost gave Buriram the lead but his strike was saved by in-form Wissanusak.
In the 78th minute, Simpson beat Muang Thong defender Arthit Daosawang and scored past Wissanusak.
Muang Thong then threw everything at Buriram. However, Simpson and Carmelo also came close to adding another goal for Buriram.
The new season of the lower leagues will begin this week while the TPL will kick off next week.