The two teams were in their first Cup final which featured four red cards, three went to Bangkok players.
Bangkok struck the first blood through a kick from Pokklaw Anan in the sixth minute before Everton Saturnino found an equalizer for Chiangrai with his header in the 25th minute.
Chiangrai surged ahead at 2-1 in the 58th minute from a goal by Rafael Coelho before Bangkok drew level again 15 minutes later by Bahrain’s international Jaycee John.
Vander Luiz of Brazil nailed the last two goals for Chiangrai who will receive a slot into the AFC Champions League play-off next year.