The American shot 66 in the fourth round to close on 12 under ahead of fellow overnight leader Roberto Castro.
Haas was firmly in control in his final round, shooting five under over his last 12 holes, making five birdies and no bogeys.
It was in stark contrast to his previous efforts on the back nine, especially the 11th where he triple bogeyed on Saturday, while on Thursday he made a double bogey, two bogeys and two birdies on the way home.
However there was to be no repeat today as he picked up his fifth title.
Castro could not stay with Haas, making a poor start with a bogey at the first, although birdies on four, nine and 14 ensured he held off the challenge from the day's big mover.
DH Lee moved up 17 places and into share of third after going seven under in his final round.
The Korean made six bogeys in his opening nine and although he dropped shots on 10 and 11, under par scores on 12, 15 and 18 saw him in as the clubhouse leader.
Jason Kokrak finished with Lee on eight under after three birdies and a bogey on the final day, while Stewart Cink was a further shot back in fifth.