Muang Thong United and BG Pathum United will face off in the League Cup final on June 16.
Muang Thong defeated defending champions Buriram United 2-0 at BG Stadium while BG Pathum edged out Port 2-1 at Ratchaburi's Dragon Solar Park in the semi-finals on Wednesday night.
Kakana Kamyok scored in the 53rd minute and Jaroensak Wonggorn added the second two minutes from time as the Kirins reached the final for the first time in seven years.
Ikhsan Fandi fired the Rabbits ahead in the 41st minute before Freddy Alvarez doubled the lead in the 62nd minute. Frans Putros cut the deficit in the 75th minute, but Port could not find the equaliser.
"We played really well during this game. The players responded to what I told them before the match that we lost to them in a league but we will not lose to them again," said Pathum coach Makoto Teguramori.
"We have to help each other to reach the final and now we have done it. This victory will give the team a lot of confidence," added the Japanese coach.
The final will be played on June 16 but the venue will be announced by the Football Association of Thailand (FAT) at a later date.
The winners of the League Cup will receive five million baht, while the runners-up will get one million baht.
Jorginho departs Buriram
Brazilian coach Jorginho has left Thai League 1 champions Buriram United with one game remaining in the current season.
His reign ended after just nine games (seven wins and two draws).
The contract was reportedly terminated by mutual consent.
Jorginho was appointed as head coach of the Thunder Castle in March, replacing Arthur Papas.
Jorginho was not present during the League Cup semi-final against Muang Thong on Wednesday night, with Emerson Pereira taking over as the team's interim coach.
Buriram will play their final game of the season on Sunday, hosting Khon Kaen United at their Chang Arena.
They were crowned champions last Friday after second-placed Bangkok United lost to Police Tero in the Angels' penultimate game.
Sivakorn to referee final
Thai referee Sivakorn Phu-udom has been selected by the Asian Football Confederation (AFC) to officiate the second leg of the AFC Champions League final match in the United Arab Emirates tomorrow.
Hernan Crespo's Al Ain will host Harry Kewell's Yokohama F Marinos tomorrow at the Hazza bin Zayed Stadium. Kewell's side won the first leg 2-1 in Japan two weeks ago.
President of the Football Association of Thailand (FAT) Nualphan Lamsam congratulated Sivakorn, the Fifa Elite referee. "It is a very proud moment for Thai referees. Sivakorn Phu-udom's selection shows that the standards of Thai referees is good and it also means that they have a great potential," said Nualphan.