Buriram climbed to third as a result of their latest triumph, which places them just three points behind leaders Muang Thong United.
Last season's champions are now unbeaten in their last nine matches in the league and their form continued with a big home triumph in round 18.
After top two Muang Thong and BEC Tero Sasana had both been held to 2-2 draws 24 hours earlier, against Osotspa and PTT Rayong respectively, Burirarm used the opportunity to close the gap.
Javier Partino's early goal put Buriram ahead and they doubled their advantage in the 27th minute through Carmelo.
And there was still time for Suchao Nuchnum to get his name on the scoresheet in the second half.
On Saturday, BEC had started the round with a disappointing draw, twice being forced to come from behind after Amadou Ouattara and Narongchai Vachiraban had given Rayong the lead either side of the break.
The reverse was true for Muang Thong, who were given a 26th-minute advantage by Erik Paartalu that was cancelled out by Chayanan Pombuppha.
Teerasil Dangda then put them ahead for a second time with 16 minutes left, only for Aron da Silva to deny them with time running out as Osotspa snatched a point.
Elsewhere on Saturday, Police United won 2-0 at Suphanburi, who lost for the first time in nine games in all competitions and dropped to fourth, while Chonburi shared a 1-1 draw with Chainat and Chiangrai United and Ratchaburi also drew, 3-3.
There was significant drama at the foot of the table as second-bottom Air Force United edged a seven-goal thriller 4-3 against Bangkok United.
Pavarit Sansook and Puwanart Sangsri both netted in the second half for Air Force.
Meanwhile, bottom-placed Samut Songkhram missed the chance to make it two wins in a row with a last-gasp 1-0 home defeat to Songkhla United.
New Zealand forward Kayne Vincent scored the game's only goal from the penalty spot in second-half stoppage time.
Other results on Sunday saw Army United play out a 2-2 draw with Sisaket, while Singhtarua edged Bangkok Glass 2-1.
