The winners of Thai League 1 will be decided on the last day of the season after leaders Buriram United leaders suffered a shock defeat on Saturday night while second-ranked Bangkok United posted a convincing victory.
Defending champions Buriram were hoping to celebrate the title at Ratchaburi but ended up returning home empty-handed following a 3-2 defeat.
Bangkok United claimed three points after a dominating 3-0 victory over third-ranked BG Pathum United.
The gap between the top two teams is now reduced to just one point with the Thunder Castle having 67 points from 29 games.
Buriram and Bangkok will play their last games of the season on April 30, with the Thunder Castle hosting Nongbua Pitchaya and the Angels visiting PT Prachuap.
The Prachuap v Bangkok match was originally scheduled to take place on April 27.
Buriram will play Al Ahli of Saudi Arabia in the quarter-finals of the AFC Champions League Elite in Jeddah on April 26, with the semi-finals taking place on April 29-30.
However, the Thai League 1 programme is unlikely be rescheduled even if Buriram make it to the last four of the continent's top club tournament, which will force the Thunder Castle to chose between the ACL and T1 events and heavily rotate their squad for the games.
Pedro Tanausu's early goal for Ratchaburi was ruled out after a VAR check but the hosts had a reason to celebrate when Jakkrapan Kaewprom put them ahead on 29 minutes.
The Dragons got their second goal in the 33rd minute from Njiva.
Five minutes before half-time, Guilherme Bissoli converted a penalty for Buriram after their defender Dion Cools was fouled by Apisit Sorada in the penalty area.
Buriram levelled the score when Bissoli set up Supachai Chaided near the hour mark, but an injury-time effort Chotipat Poomkaew denied the champions the three points they needed.
Bangkok United, on the other hand, got the result they wanted at home.
The Angels were put on course in the 34th minute by Luka Adzic before Muhsen Al Ghassani (69) and Thitiphan Puangchan (90+6) struck to make it 3-0 and give Bangkok United a realistic chance of winning their first-ever league title.
In the other games on Saturday night, hosts Sukhothai were held to a 3-3 draw by struggling champions Chiang Rai United and Lamphun Warriors played out a 1-1 draw with Nakhon Pathom United at their home ground.