Defending champions Buriram United and current Thai League 1 leaders Bangkok United both dropped points after being held to draws on Friday night.
Buriram's game with Ratchaburi ended in goalless stalemate while Bangkok United conceded an injury-time equaliser for a 1-1 draw with Nakhon Pathom United.
The Thunder Castle have now fallen six points behind Bangkok United after nine matches. The Angels, who have 23 points, are assured of another week at the top of the table.
Buriram coach Arthur Papas apologised to the fans after his men produced another disappointing result in the top flight.
"We weren't good enough in the first 10 minutes of the match but after that we played better football," he said.
"We created many chances but were not able to avail them.
"I apologise to the fans for not being able to pick up three points from this game, but we are still in a good position.
"I think this team have the potential and we are moving in the right direction."
Buriram will next take on China's Zhejiang FC in an away AFC Champions League game on Wednesday.
In another match on Friday night, Bangkok United seemed heading for a win at their home ground but suffered a late shock.
The Angels claimed the upper hand in the 58th minute when Willen Mota converted a penalty, but Nakhon Pathom's Amirali Chegini headed home the equaliser in the 98th minute of the match to steal a point from the game.
Bangkok United will next be at home to Singapore's Lion City Sailors for an AFC Champions League match on Wednesday.