Ratchaburi's campaign for the Thai League 1 title once again showed signs of running out of steam as they suffered a shock 1-0 defeat at Sukhothai on Saturday night.
A blistering strike from Swedish player Osman Sow early in the second half was all that the hosts needed to seal three points from the game.
Ratchaburi would be rueing the opportunities they missed in the first half with Derley and Alvin Fortes failing to capitalise on the chances they had.
The visitors dominated the midfield and went all out in their effort to level the score in the last 15 minutes but Sukhothai defenders held their ground well.
Ratchaburi remained in third place in the league with 16 points but have a game in hand.
Meanwhile, Buriram United coach Masatada Ishii praised his team for changing gears in the second half and claiming a 2-0 victory over Lamphun Warriors on Friday night.
It was the third straight league victory for the Thunder Castle which took them to the top spot in the table with 20 points.
Buriram netted their first goal in the 52nd minute when Jonathan Bolingi scored before Goran Causic headed in a 75th-minute cross from Naruebodin Weerawatnodom to seal three points for the defending champions.
Chonburi would now have to beat Khon Kaen United in an away game tonight to wrest back the top spot from Buriram.
Ishii admitted after the away match that he had been worried about the Warriors' defensive prowess.
"We knew that it will be a difficult game because Lamphun may not have won any match yet, but they haven't conceded many goals either," said Ishii.
"We weren't able to put the ball in their net in the first half, but I am happy that we got two in the second.
"A change in tactics after the break worked well but, to me, it is equally important that we were able to maintain a clean sheet."
Ishii also expressed his shock at the shooting incident at a daycare centre in Nong Bua Lam Phu that left 36 people including many children dead and expressed his grief over the loss of innocent lives.
In their next game on Saturday, Buriram will host Nongbua Pitchaya on Oct 15.
