Tim Petrovic fired a 4-under 66 in the second round to climb into second place. Petrovic, who is minus-9, is alone in second one shot ahead of Jeff Sluman (69), Kevin Sutherland (68), Scott Verplank (63) and Robert Gamez (66).
Play rotated over the first two rounds between the TPC at Las Colinas and Cottonwood Valley Golf Club. Action will shift to Las Colinas for the final two rounds.
Singh, who played Cottonwood on Friday, used a new putter despite opening with a 65 at the TPC at Las Colinas.
'If I used the putter I did today, I probably would have shot a 60 on Thursday if I had used it then,' said Singh. 'I missed a lot of chances yesterday. That's why I changed it.'
Singh started quickly with a birdie at the par-4 first. However the Fijian faltered with a bogey at the next. After a pair of pars, Singh birdied the par-4 fifth.
Around the turn, Singh dropped back to even par for his round with a bogey at the 10th. The 2000 Masters winner then caught fire. He ran off four straight birdies from the par-5 11th to move to minus-9. Singh capped his round with a birdie at the par-5 16th.
'I was very patient out there,' Singh said. 'I am surprised that I'm leading where I finished.'
Singh said that any controversy regarding his comments on Annika Sorenstam playing in next week's Colonial is not bothering him.
'I'm very focused. I'm came here to win the golf tournament,' said Singh. 'It's a great event. It's Byron's tournament, and I am just looking forward to playing it. My mind is totally on this golf game and that's it.'
Playing the TPC at Las Colinas, Petrovic opened with a birdie at the par-3 second. He followed that with a birdie at the par-4 fourth.
The 36-year-old then flew a 7-iron at the 184-yard par-3 directly into the cup for an ace.
'I hit it up in the air and it just flew straight in, a three-point play from 184 yards,' said Petrovic. 'The ball didn't touch the hole, it just went right in the cup, right in the bottom.'
Petrovic, who is searching for his first PGA Tour victory, parred the next four holes. Around the turn, he made his final birdie at the par-4 10th. He played the final eight holes in plus-1 as he bogeyed the par-3 17th.
'I kept playing aggressive,' said Petrovic in reference to following up the hole-in-one. 'I was shaping the ball into the green real nice and just trying to control the wind and hit the ball close. I had some good opportunities and just didn't capitalize on the back.'
Luke Donald fired a 5-under 65 to climb into a tie for seventh place at 6-under-par 134. He is joined there by Brad Faxon, Jim Furyk, J.P. Hayes, Lee Janzen, Jerry Kelly, Robert Allenby, Briny Baird and Cameron Beckman.
Shigeki Maruyama, the 2002 champion who has struggled with neck injuries since the win last year, was among those who missed the cut. The cut line fell at even-par 140 with Maruyama finishing at 1-over-par 141. John Daly (3-over) and David Duval (6-over-par 146) were also among those missing the cut.