Hidemichi Tanaka posted a 5-under 67 on Monday to take fourth place at 19- under-par 269. Justin Rose (69) and Charles Howell III (70) shared fifth at minus-17.
The tournament was plagued by weather problems all week. Friday's action was washed out completely, then part of Saturday's play was stopped due to more storms. Part of the second round and all of the third round was contested on Sunday.
Singh, ranked second in the world, came from behind last week to win the Houston Open, which also finished on Monday. His win at English Turn Golf and Country Club Monday was his fourth Monday victory along with last week, the 2003 John Deere Classic and the 1997 Memorial.
'I don't think it's Monday, I think it's the way I finished today,' said Singh, who pocketed $918,000 for the win. 'I was just hanging in there. I played a solid round of golf on the back.'
At the 18th, Singh was tied for the lead with Ogilvie with Mickelson one stroke behind. Singh's closest competitors were in the group behind so Singh had the opportunity to post the lowest score in the clubhouse.
Singh drove into the first cut on the right side but wedged his approach 35 feet short of the hole. He rolled home the birdie putt to get in at 22-under par.
'I thought I didn't hit it,' said Singh, who picked up his 18th victory on the PGA Tour. 'It had enough to get up there. I was happy to see it go in. That was probably one of the really good putts I hit all day.'
Ogilvie's tee ball went right into the rough and he hit his second into the front bunker and the scene made Ogilvie remember a past HP Classic of New Orleans.
In 1990, David Frost holed out from the bunker to defeat Greg Norman and win the title. Ogilvie mentioned that note to his caddie walking up to the sand trap.
Unfortunately, Ogilvie did not have the same fortune as Frost, although Ogilvie sure tried. He blasted out and the ball rolled toward the cup but stopped on the left edge, allowing Singh to become the first three-time winner on the PGA Tour this season.
'I'm pretty happy,' admitted Ogilvie, who shot a 4-under 68 on Monday. 'I didn't have a bogey on the weekend. It was fun coming down the stretch with Phil and Vijay.'
Mickelson sank an 18-footer for birdie at the last to shoot 66 and match Ogilvie in second place at 21-under-par 267. The runner-up finish gave Mickelson nine top-10s in 10 starts in 2004.
But now Mickelson is looking up at Singh on the money list.
Singh tallied two birdies on his first nine, but was down on the back side as it looked like Ogilvie's tournament to win. Singh ran off three consecutive birdies from the 11th to get within striking distance of the lead.
Singh got two strokes closer to the lead at the par-5 15th. He drained an 18-foot eagle putt to pull himself one shot from the lead.
At the short, par-4 16th, Singh knocked his approach to a foot and kicked in the birdie putt to match Ogilvie in the lead. One group behind Singh, Mickelson hit his second to a foot to get within one of the co-leaders, but Ogilvie hit an errant second at the 16th. His approach sailed over the green, but he chipped to two feet and sank the putt to remain tied for the lead.
Singh missed the putting surface short and right at the par-3 17th. He elected to use a putter and lagged his second three feet from the stick. Singh drained the par putt to stay at 21-under.
Ogilvie had his problems at 17. He went farther right of Singh's ball at 17, but knocked his second to roughly the same distance Singh did one group earlier. Ogilvie also made his par putt but fell victim to Singh's back-nine 29.
'That eagle putt on 15 kind of got me really fired up,' said Singh. 'And a great putt on 18.'
Stephen Ames (65), K.J. Choi (69) and Brian Bateman (69) tied for seventh at 16-under-par 272. Matt Kuchar (70) and Joe Durant (69) were knotted in 10th at minus-15.