The Beetles, on their part, went on a goal-scoring rampage at Suphanburi, thrashing the 10-man home team 5-2.
Both Chiang Rai United and the Thunder Castle ended up with identical 58 points from 30 matches. However, the Beetles were declared the winners of the league on the basis of a better head-to-head record.
Chiang Rai held Buriram to a goalless draw away in the first leg in April and then thrashed the northeastern giants 4-0 at home in July.
Chiang Rai Needed a Jolt Before they Got Going
Thanasit Siriphala pounced on a mistake by Chiang Rai’s Shinnaphat Leeaoh and set up Cleiton Silva to score near the 15-minute mark.
The Beetles, who knew they needed a victory to have any chance of winning the coveted league crown. They went all out on attack but needed almost half an hour to get level. Siwakorn Tiatrakul equalised for the visitors.
Chiang Rai went ahead early in the second half when William Henrique found the net and soon Ekanit Panya made it 3-1.
Thanasit pulled one back for Suphanburi but Chiang Rai United widened the gap again when Bill Rosimar converted a 72nd-minute penalty.
Their fifth goal of the night was claimed by Phitiwat Sukjitthammakul late in the match, the Bangkok Post reported.
Suphanburi’s fate in the top tier now hangs in the balance. In case PTT Rayong decide to continue playing in Thai League 1, Suphanburi will be relegated to the second division.
Buriram looked the better side for the most part of the first half but their lack of clinical finishing was exposed by a determined Chiang Mai defence.
Highlights of Chiang Rai United and Suphanburi
Nacer Barazite delivered again by putting Buriram ahead early in the second half. They remained on course for another title until three minutes from time when Caique — on loan from Chiang Rai. Headed home a Atthawit Sukchuay corner to hand the trophy to his parent club.
Chiang Rai United are only the third team to win the top flight after Buriram and SCG Muang Thong United. Ever since the country’s premier tournament was revamped in 2009.
In other matches; True Bangkok United routed PTT Rayong 4-0; Chainat upset Chonburi 2-1; Sukhothai escaped relegation by beating Nakhon Ratchasima 4-2; Port and Samut Prakan City played out a 2-2 draw; Prachuap were held 2-2 at home by Ratchaburi, and Muang Thong edged Trat 4-3.
Photos’ From Beetles Fan Page