'I hit a lot of close shots, but I think making those 5- , 6- , 7-footers and occasionally 10-footers, that kept the round going,' said Singh, who posted three 63s prior to Thursday's opening round. 'I was really pleased with my round.'
Olin Browne is alone in second place after a first-round 64. Mike Grob birdied three of his final four holes Thursday to vault into third place at minus-7.
Defending champion Jim Furyk carded a 6-under-par 66 and is tied for fourth place with Brenden Pappas, Len Mattiace, Craig Barlow and David Peoples.
Tiger Woods, who won this title in 2002, returned to the tour for the first time since the British Open. He shot a 5-under-par 67 and is part of group tied for ninth place.
Woods was joined in ninth by good friend Mark O'Meara, Briny Baird, Roger Tambellini, Robert Damron, Stephen Allan and last week's U.S. Bank Championship in Milwaukee winner Carlos Franco.
Woods started on the back nine Thursday and made two birdies on his opening nine. Perhaps his best hole was the driveable, par-4 14th. He crouched under a tree and somehow saved par.
He recorded three birdies on his second nine to get into position for a run at the lead.
'The greens are soft and the wind didn't start blowing till probably the last three holes for us,' said Woods. 'It was probably as easy as we've ever seen it here. That's usually not the case here.'
Rain during the week made Warwick Hills longer, but the greens were receptive.
Singh wasted little time in taking advantage of the optimum conditions.
He holed a 5-footer at No. 1 to get into red figures early, but trouble loomed for the third-ranked player in the world. He missed the green at three, then pitched to 4 feet, where he missed the par putt.
The Fijian hit a sand-wedge to 3 feet to set up birdie at the sixth, then closed out his front nine with another great wedge shot, this time a pitching-wedge to 4 feet. Singh holed that to make the turn at 2 under.
Singh made it two in a row with a 5-foot birdie putt at 10. He parred 11, but got back to making birdies at the 12th, a 6-footer after another brilliant wedge to the green.
The two-time major winner reached the par-5 13th green in two with a 3-wood. The ball stopped 6 feet from the hole and Singh ran home the eagle try to get to minus-6.
He missed the green with a driver at the par-4 14th, but pitched to 15 feet where he made his longest birdie try of the round. Singh finished off back-to-back birdies at 15 when his 8-iron approach left him with 10 feet.
Singh polished off his round with a driver-9-iron to 8 feet at No. 18 and a round of 63, which matched his lowest round in the 2004 season.
For the first time in two-and-a-half years, Singh abandoned the belly putter and used the more conventional putter.
'I was struggling. I won three tournaments and doesn't mean I'm putting badly. I was putting nicely, but then all of a sudden, I just could not make any more putts,' said Singh, who won this title in 1997. 'I decided I'm going to try it out and worked every day last week at least an hour and a half a day, just putting on it and felt comfortable.'
Browne tallied four birdies on the front side, then played well in spurts on the back nine. He made a pair of 15-footers for birdie at 12 and 13, then once again ran off back-to-back birdies.
At the par-five 16th, Browne hit a lob-wedge to 12 feet and drained the birdie putt. He used a 6-iron at the par-3 17th and canned the 8-footer to get within one of Singh's lead.
Browne has only two top-10s this season, both in the last five weeks. He recorded only two top-10s in the previous two seasons, but Browne thinks he has figured out the problems.
'When you are hitting poor shots, you start getting into a rut where you wonder if you will ever get it figured out. The minute you get it going again, you think, it wasn't that hard,' said Browne, a two-time winner on tour. 'It's not just my putter. I'm driving it better than I was.'