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.
But Theeratorn Boonmatan netted in the 71st minute to give Buriram a chance and Hirano completed the comeback with just one minute to play.
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.
Third-placed Chonburi also won over the weekend, with Thiago Cunha netting twice in a 3-0 home win over relegation-threatened Chiangrai United.
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.
It was a different story for Samut Songkhram, however, as they put distance between themselves and the relegation battle by beating BEC Tero Sasana 2-1.
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.
Elsewhere, Tot-Cat defeated Chainat 2-1 at home while Army United and Police United played out a 2-2 draw in Bangkok.
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