Goals from Spaniards Carmelo Gonzalez and David Rochela Calvo helped Buriram retain their crown with a 2-1 home victory over 10-man Police United.
Buriram, who now boast one title more than Muang Thong United, were aided by Adul Muensaman's second-half dismissal, which gave Rochela Calvo the chance to make it 2-0 from the penalty spot.
Surachart Sareepim pulled a goal back for Police United, but it was ultimately in vain as Buriram held on to secure top spot.
Alexandre Gama's side finish the campaign three points clear of Chonburi after the latter were held to a 1-1 draw by TOT.
The point was not enough to keep TOT in the top flight, with Police United staying up at their expense courtesy of a better goal difference.
Thiago Cunha gave Chonburi hope they could climb back to the top of the table with a 23rd-minute opener, but Suttinun Phuk-hom's equaliser three minutes before the hour mark saw the points shared in a game that ended with disappointment for both sides.
TOT join four other sides that had already been condemned to relegation, with PTT Rayong the only one of those to win on the final day.
Amadou Ouattara's double secured a 2-1 victory for Rayong over Bangkok Glass.
Air Force United bowed out of the top flight with a goalless draw against Chainat, rock-bottom Samut Songkhram lost their 29th game of the season when going down 4-0 to Ratchaburi and Songkhla United fell to a 1-0 defeat at Suphanburi.
Singhtarua ensured they stayed up, despite a nine-point deduction, by beating Sisaket 3-1.
Elsewhere, Muang Thong rounded off the campaign with a 3-2 defeat against Bangkok United, while Chiangrai United were 2-1 winners over BEC Tero Sasana and Army United ran out 2-0 victors in their meeting with Osotspa.