Defending champions BG Pathum United exited the Thai League Cup at the last 16 stage following a 3-1 loss to Buriram United on Wednesday night.
Hosts Buriram had an early chance but Lucas Crispim's shot sailed over the crossbar.
They got their first goal in the 32nd minute when Martin Boakye was set up by Phitiwat Sookjitthammakul with a nifty pass.
The Thunder Castle shifted gears in the second half and netted their second goal through Supachai Chaided in the 46th minute.
The Rabbits narrowed the margin when Chanathip Songkrasin passed the ball on to Raniel Santana to bundle it home.
Buriram grabbed their third goal in the 83rd minute from a penalty kick converted by Guilherme Bissoli.
The spot kick was awarded after Sasalak Haiprakhon was fouled by Pathum United's national team striker Patrik Gustavsson.
Port also progressed to the the quarter-finals after edging fellow Thai League 1 club Khon Kaen United 3-2 in hotly contested encounter.
Elsewhere, Ratchaburi beat Rayong 1-0; Nongbua Pitchaya edged Nakhon Pathom United 1-0; Chainat lost 1-0 to Bangkok United; Chiang Rai United beat PT Prachuap 1-0; Muang Trang United were beaten 3-1 by Lamphun Warriors after extra time; and Uthai Thani defeated Roi Et United 3-0.
The draw for the quarter-finals will be held on March 13 and the quarter-finals matches will be played on April 16.
The winners will get five million baht and the runners-up will receive one million baht.
