The newly crowned champions ensure they would finish the campaign without defeat as forward Suchao Nutnum scored what proved to be the winner just before the half-hour mark after Kai Hirano's opener had been cancelled out by TOT striker Kanokphol Roongrueangrotchana.
Midfielder Carmelo was sent-off for Buriram midway through the second half, but the 10 men hung on to claim the points.
Meanwhile, at the other end of the table, Pattaya United's relegation was confirmed, despite their 2-1 win at Police United.
Two goals in the space of 23 minutes from Nigerian striker Obinna Ajoku put Pattaya in command and, although forward Michael Murcy pulled one back for the hosts, they could not complete the comeback.
attaya's efforts proved futile as Samut Songkhram's 2-2 draw with Ratchaburi and Songkhla United's 2-1 win against Suphanburi made sure that they will contest next season in Division 1.
A goal five minutes from time from attacker Sulaiman Arwarekaji wrapped up the win for Songkhla, while Samut threw away a two-goal lead as second-half strikes from striker Anuwat Nakkasaem and Costa Rican midfielder Jose Luis Cordero earned a share of the spoils for Ratchaburi.
Ivorian Dango Siaka scored with four minutes to play to clinch a 2-2 draw for runners-up Muang Thong United against Chainat, who had taken the lead through a Puwadon Suwannachat brace.
Third-placed Chonburi cruised to 4-1 triumph at Osotspa thanks in part to a double from attacker Pipob On-Mo, and Brazilian attacker Cleiton Silva scored twice as BEC Tero Sasana beat Army United 4-1.
Elsewhere, Chiangrai United ended their campaign with a 4-2 over Bangkok United as both teams finished in mid-table.
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