The Dane carded six birdies and a lone bogey to move to the top of the leaderboard with a patiently crafted five-under-par 66 at the co-sanctioned $6 million event on a muggy but clear morning at the Sentosa Golf Club.
The vice-captain of Europe's victorious Ryder Cup campaign in September sits a stroke clear of Briton Simon Khan, Thailand's Chinnarat Phadungsil and Spain's Pablo Martin, who all recorded matching 67s in the early session of play.
Former world number three Paul Casey continued his late-season return to form with a three-under 68 to join South Korea's Yang Yong-eun and Thailand's Kwanchai Tannin in a tie for fifth place.
Kwanchai's compatriot Chapchai Nirat is also on three-under for the tournament but has only completed five holes of his round, three fewer than world number one Rory McIlroy, who was even par for his round when play was suspended.
The tournament has a history of weather delays and Monday finishes but the prospect of a full day's play appeared possible when Bjorn completed his round in glorious sunshine and set an early marker for the rest of the field to take aim at.
"I came here and saw the golf course, and its set-up to be tricky this year and I knew that everything was about driving the golf ball well," the 41-year-old Dane told reporters.
"It's not the longest golf course in the world so if you can keep it in the fairway, you can produce a score, and I did that very well today. That's only round one, so we'll work from here."
McIlroy, being watched by tennis-playing girlfriend Caroline Wozniacki in a role reversal from last week when he skipped the WGC-HSBC Champions event to cheer her on at a tournament in Bulgaria, bookended two birdies with bogeys on his first and last holes before the weather moved in.
The Northern Irishman and 77 other players will return to the course at 7.30 local time (23:30 GMT Thursday) on Friday to complete their opening 18 holes before the field can start their second rounds.
Casey has endured what he described as a "rubbish year" since dislocating his shoulder in a snowboarding accident last December, but the Briton recorded top-10 finishes in his last two events and was delighted to be back in the mix in Singapore.
"The golf has been very nice lately and I would like to sneak a win in before I finish my season this year," said Casey, whose poor form has seen him drop to 118th in the world rankings.
"In terms of where I stand in the rankings is pretty much a write off. I am very much focusing on next year for that aspect of my game but there are tournaments still to be won."
Edoardo Molinari was also a happy man after the Italian battled back from dropping three shots on the opening three holes to cap his one-under par 70 with a first hole-in-one as a professional on the par-three 17th.
"I hit a six-iron 188 yards and we had a decent view of it. It pitched just short of the hole and all of a sudden the people behind the green started to scream and clap," the 31-year-old said.
"I had a very bad start with a bogey on the first and a double bogey on the third but three birdies in four holes brought it back to level par. I did not hit the ball very well unfortunately," he added.
- Sports & Recreation
- Paul Casey