Singh shot a 5-under 65 at the Bay Hill course for a 36-hole total of 9-under 131. His round was highlighted by an eagle at the par-5 sixth.
Carl Pettersson was alone in second at 133 while Lee Westwood, Ken Duke and Jim Furyk shared third at 134. J.J. Henry, who tied Fred Couples for the first-round lead, was among those at 135. Couples settled for a 73 and was in a tie for 20th at 138.
Woods was also at 138 following his 68. The world's top-ranked player, winner of this tournament four straight years beginning in 2000, has captured four straight PGA Tour events dating to last season. He is unbeaten in three starts this year -- one of those coming in Dubai.
"I'll have to play better and make a lot more putts than I have been," Woods said. "I just never got the speed of these things (the greens) today."
Phil Mickelson, second to Woods in the world rankings, shared 29th place at 139.