Bill Rosimar scored a hat-trick as Chiang Rai United defeated Chonburi 3-2 to hand the Sharks their first loss of the season in Thai League 1 on Friday night.
Bill opened the scoring within two minutes and added two more goals after 64 and 87 minutes.
Kritsada Kaman (42) and Kroekrit Thaweekarn (45) were on target for the hosts, who thrashed Khon Kaen United 7-0 last week.
Chonburi's Junior Eldstal was sent off in the 66th minute, paving the way for the Beetles to make a comeback from a 2-1 deficit.
In Saturday's action, Port will try to bounce back when they host SCG Muang Thong United.
Port took the lead in the opening minutes against Suphanburi last week only for the opponents to rally for a 2-1 win after the former were reduced to 10 men.
But Port coach Dusit Chalermsan chose to look on the bright side, saying they were not too far from the leaders.
"The next game, we cannot make similar mistakes again," said Dusit, whose team have five points from four matches.
"There are several aspects that we need to improve. In the game against Muang Thong, we must get three points. We have to regain our confidence as soon as possible."
Muang Thong also have five points after beating Ratchaburi last week.
Muang Thong coach Mario Gjurovski said the win boosted his men's confidence.
"We hope to get a good result at the PAT Stadium. We are lucky that we don't have injured or suspended players," Gjurovski said.
