Third seed Raonic took full advantage of his big serve to beat his Czech opponent, firing 18 aces -- his last to set up a pair of match points.
After winning the first set in a tiebreaker, the Canadian tightened his grip in the second to earn the fifth title of his career, converting his first match point with a down-the-line winner after 77 minutes.
His second title of the season, after San Jose in February, will serve him well in the points chase to a possible place in the eight-man ATP World Tour Finals in London in November.
Raonic also beat Berdych at their only previous meeting, in Cincinnati in 2012.
Berdych, the only member of the ranking top 10 without a title in 2013, admitted he was out-played in the Thai final.
Raonic, who has reached nine finals, has achieved all of his five trophies on his favoured fast hard courts.
The Canadian went one win further than his new coach, Croatian Ivan Ljubicic, who played the final in Bangkok in 2006 but lost.
Berdych is defending finalist points next week in Tokyo, where he is seeded third behind Juan Martin del Potro and Jo-Wilfried Tsonga. (AFP)
