The 21-year-old trailed leader Alex Noren of Sweden by five strokes Friday at the halfway stage of the penultimate tournament in the Road to Dubai series.
But while Noren faded to a 75 Saturday, Wang snatched six birdies and an eagle while not dropping a shot over the 7,161-metre (7,831-yard) layout in north-west South Africa.
His 64 was the lowest round of the week, bettering by two strokes the second-round 66 of former British Open champion Louis Oosthuizen of South Africa.
Wang was delighted that his eight-under-par round came in challenging conditions.
"I am so happy that I shot a 64 today and I am even more happy that I did not have any bogeys," he told reporters.
"To shoot eight under on this difficult course in this wind -- I still cannot believe it.
"I do not want to think now about winning this tournament. I just want to focus on the last 18 holes. I will try to play as well tomorrow."
The Korean has two European Tour victories to his credit, is ranked 91 in the world and lies 39 in the Road to Dubai standings.
Wang is on 205 in pursuit of the $1.16 million (1.03 million euros) first prize with Oosthuizen on 208 after a 70 and Andy Sullivan of England on 209 having carded a 68.
Oosthuizen teed off at 17 well placed having picked up five birdies and conceded just one bogey, but a bogey-bogey finish on two par-fours spoilt his round..
"It was a tough day again because the wind was even worse than yesterday," said Oosthuizen.
"I played well. I would have been a lot calmer right now if I was one behind. But I played nicely.
"It is not nice finishing like that (two bogeys), but I am hitting the ball well. So I am looking forward to tomorrow."
Sullivan recovered from rollercoaster bogey-birdie-bogey start to pick up five more birdies while not dropping any more shots.
South African Branden Grace, who fired a 71, and Noren are on 211 and those one shot further back include reigning British Open champion Henrik Stenson of Sweden after a 69.
Stenson topped the Road to Dubai standings going into the Nedbank Challenge, which is popularly referred to as the African Major.
