Brenden Pappas, who won the The Rex Hospital Open two weeks ago, also carded a 67 to remain alone in second place at minus-14. Joel Kribel is one stroke behind Pappas at 13-under-par 203 after a 66 in round three.
Parker McLachlin is in fourth place at 11-under-par 205 thanks to a 4-under 68. Jason Caron and Matt Hendrix are one stroke further back at minus-10.
Haas came flying out of the gates with birdies on each of the first three holes. At the first, he two-putted for birdie on the par-5.
Then on two, Haas knocked his approach to 8 feet to set up his second birdie. He followed that with a 30-foot birdie putt on Fox Den Country Club's third hole to move to minus-14.
Haas, however, gave a stroke back to par as he stumbled to a three-putt bogey on the fourth. The native Texan recovered that stroke with a birdie on the par-4 seventh.
The 28-year-old started the back nine well. Haas birdied the par-5 10th after chipping his third to 2 feet, then made it two straight as his 3-foot birdie putt at 11 found the bottom of the cup. He closed with seven straight pars to finish at 16-under.
'I was kind of disappointed at bogeying four after birdieing the first three holes,' Haas stated. 'But you shouldn't be disappointed about 5 under any time. I just have to go out there Sunday and push the guys behind me to make mistakes.'
Haas has history on his side. Eight of the 13 third-round leaders have gone on to win this event.
Pappas drained a 35-foot eagle putt on the par-5 first to get within one of Haas at 11-under. He later dropped in a birdie effort on the par-5 fifth.
The 38-year-old kept rolling on the par-fives. Pappas birdied the par-5 10th from 10 feet out to move to 13-under, two back of Haas. After a Haas birdie on 11, Pappas again was two back as he birdied the par-4 12th.
Pappas slid three back after a bogey on No. 14. He recovered that stroke with an 8-foot birdie putt at 17.
'It was a difficult day. I made all of my putts, but couldn't hit it out of my shadow,' Pappas admitted. 'I made a lot of key putts for par during the round. I was trying not to work hard today because I'm going to have to work tomorrow to catch Hunter.'
Franklin Langham carded a 4-under 68 to move to 8-under-par 208. He stands alongside Gary Christian (69), Steve Marino (69) and Boo Weekley (70) in a tie for seventh. Richard Johnson, Hiroshi Matsuo, Tim O'Neal, Chez Reavie, Jim Rutledge and Michael Boyd are one shot back at minus-7.