The $6 million co-sanctioned tournament has suffered three lengthy suspensions due to heavy thunderstorms but Bjorn returned to the Serapong Course on a rare dry afternoon to move to nine-under 133 after 36 holes with a bogey-free second round.
The Danish Ryder Cup vice-captain has not dropped a shot in 24 holes and the 41-year-old attributed the low score to his accuracy with the driver.
"This course doesn't really offer you that many wedges," he said. "Your mid-irons have to be on but driving is also essential on this course. You need to get off the tee well and I've done that for two days, and long may it continue."
South Africa's George Coetzee registered an eight-under 63, the lowest score of the week, to surge up the leaderboard into a tie for second place with Briton Chris Wood, who was almost as impressive in recording a six-under 65.
Starting on the 10th hole, Coetzee's round was highlighted by a run of six birdies in eight holes but the 26-year-old lamented a string of missed opportunities that could have put him in a stronger position.
"When I was standing on ninth green (his last), I thought to myself, 'I lipped out on five, six, eight and nine.' If I'd made all of them it could have been 10 in a row," he said, mindful of the fact that another delay could lead organisers to reduce the event to 54 holes.
"I'm quite happy with the way things are going and I'm enjoying the game. There's another round to go, at least, and I'll be giving my best."
Italy's Francesco Molinari sits alone in fourth place on six-under for the tournament, one clear of Briton Simon Dyson and Australia's three-time Singapore Open winner Adam Scott, who fired a bogey-free 66.
World number one Rory McIlroy admitted to being frustrated by the constant weather delays but the Briton shot a second successive one-under 70 to languish seven shots behind Bjorn and facing a mammoth task to even secure a top-three finish that would wrap up the European Tour order-of-merit crown.
"The course is not easy but especially having to go out and come back in. It's been a frustrating few days," McIlroy said.
"Obviously it would be nice to play a nice stretch of golf and not have to stop and start all the time but that's just the way it is and I have to deal with it but I'm pretty pleased with my two-under."
Another player happy with his day's work was Phil Mickelson after the American produced a sublime chip between two palm trees on the 18th that rolled to within six feet to ensure he got the birdie he needed to make the cut at one-over par.
"I hit one of the best tee shots I have hit all week and one of the worst second shots I have hit all week with the five wood. I don't even know what happened there," he told reporters.
"It was one of the best chips... I had to go through the trees and run it up the hill. I hit it really well and made birdie and hopefully have given myself a chance."
Malaysia's Danny Chia conjured up a miracle shot of his own to also make the cut when he aced the par-three 17th to become the third player in as many days, after Edoardo Molinari and Juvic Pagunsan, to register a hole-in-one.
The third round is now underway.
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