Chonburi stunned Buriram United 2-1 in the FA Cup semi-finals last night.
In Sunday's final, the Sharks will meet Chiang Rai United who beat Bangkok United 2-1 in the other semi-final.
At Thammasat Stadium in Rangsit, Worachit Kanitsribampen opened the scoring for Chonburi after 25 minutes only for Supachok Sarachat to equalise three minutes later.
Buriram goalkeeper Siwarak Tedsungnoen fumbled what appeared to be a soft free-kick allowing Junior Eldstal to score from close range in the 59th minute.
Buriram, who were runners-up in the 2020-21 Thai League 1 season, then threw everything at Chonburi but failed to break their defence.
At Bangkok's Boonyachinda Stadium, Chiang Rai went ahead after 38 minutes thanks to a Chaiyawat Buran strike.
Bangkok United's Mika Chunuonsee made it 1-1 in the 74th minute.
Brazilian striker Bill Rosimar scored the winner for the Beetles in the 86th minute.
Chiang Rai and Chonburi will try to win their third FA Cup title when they meet at Thammasat Stadium on Sunday.
The champions will get five million baht in prize money and a ticket to the 2022 AFC Champions League group stage.
Meanwhile, the Asian Football Confederation (AFC) plans to launch a women's Champions League in 2023 to further boost the women's game across the continent, the continental governing body said.