Hosts Nongbua Pitchaya improved their chances of survival in the top-flight with a 1-0 upset of PT Prachuap in the Thai League 1 second leg opener on Friday night.
Nongbua got the winning goal in the last minute of the first half from Norraseth Lukthong, who slotted home a cross from Paolo Conrado to help the home team pick up three points.
After the game, Nongbua Pitchaya assistant coach Supachart Manakit said: "It was a good show by our players as they executed the game plan very well.
"Prachuap are a good team and they controlled most of the game, but our players just stuck to the tactics and did well to choke Prachuap forwards.
"During the second half, we changed some tactics. In the defence, we prevented their crosses from reaching their strikers, and our goalkeeper was also great today as he saved many shots."
Meanwhile, the two top sides in Thai League 1 -- Bangkok United and Buriram United -- go head-to-head Sunday night.
The match will be played at BG Stadium, starting 7pm.
Bangkok United hope to start off the second leg by picking at least a point in their home ground, but the Thunder Castle will be eager to extend their lead.
The Angels have strengthened their squad by signing Prataman Arhan and Jakkapan Praisuwan, while Buriram United have added seven new players to their squad, including Thailand star Suphanat Mueanta.
Buriram will take the field as heavy favourites after their dominant performance in the Shopee Cup recently.