Table-toppers Buriram – who lead Muang Thong United by just three points – have not tasted defeat once this season in 29 league matches.
That record looked in serious danger after goals from Rattana Petch-Aporn and Jhon Obregon gave lowly Ratchaburi a comfortable lead on Sunday.
Alejandro Menendez's side have seen their advantage at the top cut to just three points as a result though, as Teerasil Dangda's hat-trick fired Muangthong United to a 3-1 win at Osotspa on Saturday.
Anthony Moura struck just before half-time to cancel out Dangda's first, but the hosts were powerless to prevent the 25-year-old capping an excellent performance in the second half.
Pattaya United failed to fully capitalise on struggling Chiangrai's defeat, as they were held to a 2-2 draw by Songkhla United at Nongprue Stadium.
Cleiton had given seventh-placed BEC the lead in the first half, but Samut Songkhram showed remarkable fight to claim the win through goals from Guy Hubert and Phuvanart Sangsri.
At the other end of the table, Suphanburi beat Bangkok Glass 1-0 thanks to a Dragan Boskovic penalty to replace them as the league's fourth-placed side.
