One stroke clear at the start of another blustery day at the Kapalua Resort, the Fijian birdied the first two holes before reaching the turn in two-under 34.
That left him at 13 under overall in the PGA Tour's season-opening event and comfortably ahead of playing partner Adam Scott of Australia, who was alone in second place.
South Africa's Trevor Immelman, the Tour's 2006 rookie of the year, was a further shot back in third, after nine holes, with Americans Will MacKenzie and J.B. Holmes tied for fourth at seven under.
Former world number one Singh, runner-up at Kapalua's Plantation Course twice in the last three years, made a fast start.
He struck his approach to just five feet at the par-four first to set up birdie number one before holing an 11-footer at the difficult par-three second.
The three-times major winner parred the next seven holes to stay on track for the first victory in the PGA Tour's much-trumpeted new era of golf.
This week's event launches the inaugural FedExCup, a season-long points competition culminating in a four-event playoff series with $10 million to be won by the overall champion.
Should Singh triumph at Kapalua, he would move past Sam Snead as the PGA Tour's most prolific winner after the age of 40.
At the start of this week, Singh and Snead were level with 17 titles apiece.
MacKenzie, who gave up golf for almost a decade after his sophomore year in high school, made the first significant challenge to Singh's lead.
After bogeying the opening hole, he reeled off three consecutive birdies from the second to close to within four shots Singh.
The 32-year-old from North Carolina, a professional kayaker who enjoys snowboarding and surfing, then fell back.
He bogeyed the par-four sixth, after duffing his approach and overshooting the green, and also dropped at the par-five ninth.