Leaders Buriram United suffered a shock 2-1 defeat at home to PT Prachuap that dented the Thunder Castle's dream of extending their advantage at the top of Thai League 1 on Sunday night.
Buriram were off to a good start as Phansa Hemviboon put them ahead early but Prachuap struck twice in the second half to deal the blow.
Willen Mota converted a 78th-minute penalty for the Wasps and Patrick Reichelt grabbed the match-winning goal seven minutes later.
Also last night, bottom-placed Chiangmai United pulled off a rare win as they defeated 10-man Samut Prakan City 2-0 at home.
Bill Rosimar picked up the opening goal in the first-half injury time and Sirisak Faidong sealed three points for the hosts with a strike in the 57th minute.
Chiang Rai United edged Chonburi 1-0 at home with Shinnapat Leeaoh providing the winner early in the second half.
Meanwhile, under-pressure Port coach Sarawut Treephan questioned his players' mentality after their 2-1 away loss to bitter foes Muang Thong United on Saturday night.
Willian Popp struck early in the first half before Teeraphol Yoryoei drilled home another 20 minutes after the break to give the Kirins a 2-0 advantage. Go Seul-Ki netted Port's only goal in the 71st minute.
After the match, Sarawut made no effort to hide his frustration.
"We conceded two easy goals from corner kicks," said the Port coach.
"I realise that our players are exhausted after playing two matches in the past few days and they were not efficient enough tonight.
"They are not in a good frame of mind at the moment -- they are not doing what everyone expects from them. This would have to change soon."
In the other late game on Saturday, title-contenders Bangkok United were held to a goalless draw by struggling Ratchaburi.
