In a 43-minute battle, fifth seed Prannoy, who finished runners-up at the USD 50,000 Vietnam Grand Prix in Hochiminh City last week, got the better of qualifier Firman 21-11 22-20 in the men's singles competition.
The 22-year-old Prannoy dished out a dominating performance in the opening game as he opened up a 6-2 lead early on and then kept increasing the distance. He then reeling off five straight points to take a lead 1-0 at the GOR Jakabaring stadium.
However, Firman clawed back with four straight points to draw level at 20-20. Prannoy then dug deep to reel off the next two points to seal the door on his opponent and celebrate his first title victory.
Prannoy won a silver medal in Boys' singles at 2010 Summer Youth Olympics.