Ben Curtis, the 2003 British Open champion, and Robert Allenby finished their rounds of 67 late in the day. They were joined by Pat Perez, Cameron Beckman and Richard S. Johnson in a tie for second at 5 under par. Kevin Na was at 5 under through 14 holes when play was called.
Fog delayed play in the morning at Nemacolin Woodlands Resort, pushing tee times back throughout the afternoon. The first round will resume Friday at 7:15 a.m. ET.
Singh has continued his winning ways since he assumed the top spot in the Official World Golf Ranking. He overtook Tiger Woods in the rankings with a win at the Deutsche Bank Championship and won the following week at the Canadian Open. After a couple of weeks off, Singh was back to business in search of his eighth victory of the season.
'I do the same thing over and over again with my golf swing,' said the reigning PGA champion. 'The more I do it, the better it gets. I think now my swing is into a plane where if I just keep doing what I'm doing it should stay the same.'
Singh waited through the delay to start his round and when he finally took the course he picked up a quick birdie after his approach to the second stopped within 6 feet of the hole. At the par-5 fifth, Singh bounced his second shot up close and converted the short eagle putt to reach 3 under.
'The delay kind of messed everybody up,' said Singh. 'It kind of threw you rhythm off a little bit. But it was good for me. I went out there and I played really good.'
The 41-year-old found a greenside bunker with his second shot to the par-5 eighth, but hit out of the sand to 3 feet for another birdie. Singh then hit his approach to 7 feet for a birdie at the ninth to move to 5 under around the turn.
Singh was just as steady on the inward half with a birdie at the par-4 13th. He then chipped his third shot from just off the green to 5 feet for a birdie at the par-5 16th and closed his round with a birdie at the last after his second shot stopped within 12 feet of the hole.
'I'm swinging the club as good as I think I can,' said Singh. 'I don't know if I can hit it any better. I'm doing the same thing over and over again.'
Perez managed a birdie and a bogey on the front side but the 28-year-old torched the back nine with five birdies to finish three shots off Singh's pace.
'I'm not surprised the guy that did it, did it,' Perez said of Singh's 64. 'It is out there though. If you can fly it where you want to fly it, you can get it close. If you're not right now, it's real difficult to get it close.'
Johnson started on the 10th and mixed seven birdies with two bogeys for his 67 while Beckman was bogey-free with five birdies in his round.
John Daly, Joey Sindelar, Lee Janzen, Jonathan Byrd, J.P. Hayes and Tommy Armour III are in the clubhouse at 4-under-par 68. Kris Cox was at minus-4 through 14.
Former Masters champion Mike Weir, Zach Johnson and Justin Rose are in a group at 3-under-par 69.