Muang Thong United prevailed 2-1 over Chiang Rai United at home in a clash of former Thai League 1 champions on Saturday night.
The victory pushed the Kirins' total up to 35 points from 20 matches, while the Beetles remained dangerously close to the three-team relegation zone with 23 points from 21 games.
Chiang Rai were given the advantage in the 38th minute when Sittichok Kannoo failed to gather a pass and the ball landed in front of Harhys Stewart to shoot home from close range.
Muang Thong levelled in the first-half injury time when Theerapol Yoeiyoi bundled home a nifty pass from Poramet Arjvilai.
Purachate Todsanit was instrumental in setting up the winner for the Kirins, lobbing a cross to Aly Cissokho to secure three points for the home team with a last-gasp header.
Muang Thong United assistant coach Uthai Boonmoh admitted his team were "lucky to win the match. The winner came in injury time."
In the other match on Saturday night, hosts Nakhon Ratchasima share a point with Ratchaburi following a 1-1 draw.
Pedro Tada converted a 28th-minute penalty but it was cancelled out by Swat Cats' Carlos Lima after 88 minutes.