Chiang Rai United edged Chonburi 4-3 in a pulsating penalty shoot-out following a 1-1 stalemate after extra time in the FA Cup final on Sunday night.
For Chonburi, Eliandro and Kroekrit Taweekarn were the culprits as they missed from the spot, while Shinnaphat Leeaoh failed to convert the fourth shot for the Beetles.
The third-time FA Cup champions received five million baht in prize money and, more importantly, earned a place in the 2022 AFC Champions League group stage where they will be joined by this year's Thai League 1 winners BG Pathum United.
Buriram United and Port have qualified to take part in the qualifying play-offs of the Asian club competition after finishing second and third in the top flight, respectively.
Chiang Rai edged Bangkok United 2-1 with Bill Rosimar scoring the winner to make it to the title showdown, while Chonburi shocked hot favourites Buriram United by the same scoreline in Wednesday's semi-finals.
No spectators were in sight at Thammasat Stadium last night as the match was played behind closed doors after a new wave of coronavirus cases started spreading rapidly across the country.
The Beetles entered the final as heavy favourites based on their performance in the recently concluded Thai League 1 but Chonburi were able to match them for most part of the match.
And Chonburi defender Chatmongkol Ruangtanaroj's 31st-minute goal did not surprise many as they expected an all-out effort from the Sharks in the wake of their shock semi-final win over Buriram.
Attacking midfielder Sivakorn Tiatrakul restored parity in the 41st minute for Chiang Rai and the two sides went into the breather tied 1-1.
Chiang Rai's Bill and Phitiwat Sukjitthammaku and Worachit Kanitsribumphen of Chonburi missed opportunities to score after the break and a goalless second half forced the match into extra-time.
Chonburi were the more attacking side during the extra time and came close to grabbing the winner on a couple of occasions.
As the clock ticked towards the 120-minute mark, players from both sides started showing signs of fatigue with prolific Chiang Rai striker Bill needing treatment on the sidelines, taking the steam out of the Beetles' attacks.
The ageing Brazilian was substituted a few minutes before the end of the extra time.
Worachit failed to beat Chonburi goalkeeper Saranon Anuin with a last-gasp effort from close range and a penalty shoot-out followed.
Prior to last night's clash, Chiang Rai and Chonburi had each won the tournament twice.
Chiang Rai emerged as a force to be reckoned with when they claimed their first FA Cup title in 2017 before retaining the coveted trophy the following year as well. The Beetles then went on to capture the Thai League 1 crown in 2019 to go with their success in the 2018 League Cup.
Chonburi won the league title in 2007 before the competition was rebranded in 2009. The Sharks have won the FA Cup twice in 2010 and 2016 although their last success was unique as all four semi-finalists were declared joint champions following the passing away of His Majesty King Bhumibol Adulyadej The Great.
The coronavirus-hit domestic season will come to end with the last game of the Thai League 2 promotion play-offs home-and-away final between Nakhon Pathom and Khon Kaen United on April 24. The winners of the final will be promoted to the top flight.