'I wanted to start the year off strong, and this is a great week to start,' Singh said. 'You've got no cut. You can go out there and try to do things that you don't normally do in a regular tournament. This is a huge tournament, and you know the field is very good. All of the winners are here, so it's a good one to win.'
Australian Craig Parry is alone second place at 6-under-par 67.
Tiger Woods, the world No. 2 and two-time winner of this event, is one stroke further back at minus-5. He was joined in a tie for third place by Stewart Cink, Sergio Garcia and Jonathan Kaye on the Plantation Course at Kapalua Resort.
This event is reserved for the tournament winners from the 2004 season. Of the 32 eligible players, 31 are playing this week with Masters champion Phil Mickelson skipping the tournament.
Singh is coming off a record-setting season in which he won nine titles and collected a tour record $10,905,167 in earnings. He wasted no time in getting into red figures as he rolled in a 15-foot birdie putt at the third.
The Fijian two-putted for birdie at the par-5 fifth. Singh parred his next four holes before catching fire on the back nine. He moved to 3 under with a 6-foot birdie putt at the 10th.
Singh made it two straight as he converted his birdie attempt at the par-3 11th. The reigning PGA Championship winner made it three in a row as he birdied the 12th to climb to minus-5.
After a pair of pars, Singh finally moved ahead of the field with a 3-foot birdie putt at the par-5 15th.
The world No. 1 came right back with a birdie at the next from 8 feet out to climb to 7 under. Singh closed with a pair of pars to hold the lead at an event he has yet to win.
'I played really well. I left quite a few out there, but everybody must have done the same,' said Singh. 'I drove the ball well and hit a lot of greens. I putted well, too. So it was a good day.'
Parry was hot through the front nine before cooling around the turn. The Australian ran off three consecutive birdies from the par-4 third. He picked up another birdie at the seventh to move to minus-4.
The 38-year-old Parry, who last year holed out from the fairway for eagle on the first playoff hole to win the Ford Championship at Doral, got to 5 under with a birdie at the ninth. He followed with a birdie on 10 to take the outright lead.
Parry, however, stumbled to a bogey at the par-4 12th. He closed with a birdie at the last to claim second place.
'I got off to a good start on the front nine,' said Parry. 'I had a few opportunities from about 12 or 15 feet and made them, and obviously that gave me the momentum to get going. On the back nine, I hit one wayward shot on No. 12 and made bogey.'
Woods wrapped birdies at the third and fifth around a bogey at the fourth. The 29-year-old got to minus-2 when he birdied the par-5 ninth. Like Parry and Singh, Woods also collected a birdie on No. 10.
The 2004 WGC-Accenture Match Play Championship winner continued his climb up the leaderboard as he birdied the par-4 13th. Woods capped his scoring with a birdie on the par-5 15th.
'I felt like I played well,' Woods said. 'I hit a lot of good shots, but didn't really make a lot of putts. I took care of the par-5s and hit a few in there close. But outside of that, I didn't really make any putts.'
Ernie Els, a three-time winner in 2004, posted a 4-under-par 69 to hold a share of seventh place. He was joined there by Bay Hill Invitational winner Chad Campbell as well as Woody Austin, Bart Bryant, Steve Flesch, Adam Scott, Heath Slocum and Vaughn Taylor.
John Daly, Mark Hensby, Rod Pampling and Mike Weir are one stroke further back at minus-3.
U.S. Open champion Retief Goosen posted a 2-under-par 71 and British Open champion Todd Hamilton is one stroke behind him at minus-1.
Defending champion Stuart Appleby struggled to a 1-over-par 74.