Leaders Buriram United failed in their bid to secure the Thai League 1 title in front of their home crowd after being held to a 1-1 draw by Port on Sunday night.
The northeastern giants are now five points ahead of Bangkok United, who blanked Trat 5-0 at home on Sunday night, with just six points available from the two remaining games this season.
The Thunder Castle were made to work hard after they conceded a first-half goal -- a 21st-minute strike by Worachit Kanitsribampen.
The defending champions drew some loud cheers from their fans when Guilherme Bissoli produced the equaliser near the hour mark.
Buriram coach Jorginho was not flustered by the outcome, saying his men would try to finish the job away in Uthai Thani on the next weekend.
"We played very well, and this time we were up against a strong opposition," said the Brazilian coach.
"We were in control throughout the first half and created as many as four scoring opportunities. It was our bad luck that we conceded a goal on the only counter-attack they [Port] launched.
Meanwhile, it was a one-way traffic at Bangkok United's home ground as the Angels fired five unanswered goals past Trat on Sunday night.
The victory has kept Bangkok United's slim mathematical chance of claiming their maiden Thai League 1 crown alive.
Willen Mota was the star of the night as he produced a hat-trick for the Angels.
In another match on Sunday night, Chonburi were held to a 1-1 draw at home by PT Prachuap.