Ubon UMT United playmaker Bajram Nebihi struck a brace to help his side win 3-2 at Muang Thong United to complete a miserable week for the Thai League (T1) champions.
Totchtawan Sripan's side's defeat was their third in six days, meaning the worst possible preparation for their AFC Champions League (ACL) Round of 16 clash with Kawasaki Frontale on Tuesday.
Buriram United failed to take full advantage of Muang Thong's latest slip as they were held at BEC Tero Sasana, but they still managed to draw level with their rivals.
Here are five things we saw on T1 Matchday 16:
1. Ubon pile on the agony for Muang Thong
Ubon UMT United's victory ensured that Muang Thong United have lost to all three teams who were promoted from League Two in a week. That's after last weekend's 1-0 defeat at Thai Honda and Wednesday's 3-2 loss at home to Port FC.
On Saturday, the hosts were stunned when Nebihi surged into the box before firing past Kawin Thamsatchanan in the fourth minute. Theerathon Bunmathan levelled from the penalty spot in the 57th minute, and the Kirins were then expected to push on and win.
But Victor Cardozo quickly put the visitors back in front and Nebihi grabbed his second in the 70th minute. Teerasil Dangda pulled one back in added time, but Muang Thong were beaten at home for the second time in four days.
The victory was a triumph for former Muang Thong head coach Scott Cooper. Nebihi admitted that the Englishman had played a key role.
"Our coach motivated us and gave us a lot of confidence for the game," Nebihi told ESPN FC. "We were all ready to fight from the first minute and to show we can play good football and enjoy the game, the stadium and the atmosphere."
Ubon were the league's surprise package when they won their first three games of the season, but form has since been more inconsistent.
"We are a new team in this league, and that's why sometimes we lost some games very unluckily, but we learn from this and will get better," said Nebihi. "We have had a good season so far and, in the second leg, I hope and think we will be more confident and finish the year in a good position."
2. Buriram blow chance to pull clear
Muang Thong United's slump gave Buriram the chance to go two points clear at the top on Sunday. But the Thunder Castle failed to make the most of their opportunity as BEC Tero Sasana held them to a 2-2 draw.
The visitors took an early lead through Diogo Luis Santo. But Michael N'Dri levelled with a penalty before the Frenchman set Wichan Nantasri up for Tero's second. Diogo grabbed Buriram's equaliser, but they couldn't find the all-important winner.
Buriram boss Ranko Popovic was furious with the referee, and refused to take questions from reporters after the game.
Tero striker N'Dri, on the other hand, felt that his side might have deserved more than the point they earned.
"We played well but made two mistakes and were punished by a quality team," N'Dri told ESPN FC. "Overall, I think we deserved three points. Against a team like Buriram, a draw is a good result, but on the balance of play, I think we should have had more.
"We have had a good first half of the season and, particularly at home, we have demonstrated that we're a tough team to play against. No team has beaten us convincingly and I hope that continues until the end of the season."
3. Chiang Rai back in business
With Muang Thong losing, and Buriram drawing, Chiang Rai United made the most of their good fortune to move a point off the lead with a 1-0 win at Nakhon Ratchasima.
A dull game appeared to be heading for the Swatcats' fourth goalless draw in six matches until Felipe Azevedo netted his 11th goal of the season in the 81st minute.
The Brazilian's late intervention proved crucial, and results elsewhere, heightened its importance. The Beetles' title challenge looked over last weekend after a run of three games without a win. But the points dropped by their rivals have allowed Alexandre Gama's men the chance to dream of glory again.
4. Pattaya stun Bangkok Glass
Pattaya United have been one of this year's most unpredictable teams. Two weeks ago, they outplayed Port FC in Bangkok and came away with a 2-0 win. But they followed this up with a disappointing defeat at home to Ubon UMT United before a second-half collapse saw them lose 4-1 at Chiang Rai United in midweek.
But the Blue Dolphins brought their A game on Saturday as they dismissed Bangkok Glass 4-2. Lee Won-Young's header gave the hosts an early lead and Chainarong Tathong made it 2-0 in the 19th minute.
Chatree Chimtalay continued his fine scoring form by pulling one back for Bangkok Glass. But Woranat Thongkruea's long-range effort restored Pattaya's two-goal advantage before Mongkol Namnuad's red card left the visitors a man down.
Peeradol Chamratsamee added a fourth for the home side and Daniel "Toti" Rodriguez's excellent late strike for Bangkok Glass was little consolation for the visitors, who missed an opportunity to close to within a point of faltering Muang Thong.
5. Leandro heroics lift Sisaket
Leandro Assumpcao scored his second hat trick of the week to take Sisaket to within a point of opponents Thai Honda as the Koupreys came from 2-0 down to win 3-2.
It all looked good for the hosts when Decha Sa-ardchom's screamer gave them a early lead before Thawin Butsombut -- provider of last week's winner against Muang Thong -- swiftly added a second.
But 34-year-old Leandro followed up his midweek hat trick in the 4-2 victory over Navy FC, with another treble, the winning goal coming in the second minute of added time. The former Chonburi striker netted a fine free kick to bring the visitors back into the game before the equaliser was deflected in.
There were chances at both ends before an excellent turn and shot from 18 yards out earned a much-needed three points for Velizar Popov's side.