Buriram United outplayed Port 3-1 Sunday night, and, barring a major upset, the Thunder Castle look set to celebrate their seventh Thai League 1 title on Saturday.
Chiang Rai United also put on an impressive show at home where they trounced 10-man PT Prachuap 4-1, but their commendable effort could come up a couple of points too short.
While the Beetles will now be plotting ways to tame Suphanburi on Saturday, Buriram will play their last game against bottom-placed Chiangmai.
Chiangmai, despite a rallying 3-2 victory away at PTT Rayong, were condemned to a return to the second tier Sunday night.
The northern minnows, who could not survive their first and only top-flight test, do not look capable of stopping the mighty Buriram juggernaut loaded with national team stars and expensive imports.
Chiang Rai, on their part, can expect an all-out effort from Suphanburi, who will be fighting for their survival in the elite division on Saturday.
Sergio Suarez gave Port hope for their first ever victory at Buriram's home ground in the 20th minute, but Nacer Barazite tapped home a Naruebodin Weerawatnodom cross to level the score shortly after the 30-minute mark.
Supachok Sarachart broke free from Port defenders two minutes later and grabbed the second for the hosts before Kevin Ingreso made it 3-1 with a free-kick in the 71st minute to push Port out of the title race.
Suphanburi pulled off a fighting 3-2 victory away at Samut Prakan City Sunday night which steered them one point clear of the three-team relegation zone.
True Bangkok United squandered a two-goal advantage to allow hosts Ratchaburi to salvage a 2-2 draw and Chonburi fired two unanswered goals past SCG Muang Thong United.
Sukhothai remain precariously placed despite a 2-1 home win over Trat, but visiting Nakhon Ratchasima confirmed Chainat's drop to the lower division following a 3-1 rout.