The Australian had started the day with a two shot lead but was dragged into an epic tussle with playing partner Poulter down the back nine of the Serapong Course, the 2005 and 2006 winner eventually emerging with the narrowest of leads.
The 30 year old signed for a round of 69 to sit 14 under par, while Poulter carded two birdies and an eagle in a round of 68.
"It wasn't easy out there today," said Scott. "It was hot and it was a long round and I wasn't feeling on top of a lot of aspects of my game at times but I am just happy to have got back to the clubhouse with 69 which is always a good score - it's respectable."
Poulter was pleased to have reduced the deficit after a round which took over five hours to complete.
"I played nicely," said Poulter, who held off China's Liang Wen-chong in the final round 12 months ago.
"I think I missed one green and that was about five feet out so I actually hit about 18 greens in regulation. But Adam played well as well so I think tomorrow is going to be a great day."
World Number 567 Kang is also right in the frame having seemingly been out of the running when he ran up a double bogey seven at the seventh - only to respond with a brilliant back nine 30 which included five unanswered birdies.
Both Scott and Poulter opened their accounts with birdies at the par three second, the Englishman hitting his tee shot to within six feet.
But Scott bogeyed the next and despite a birdie at the par five fourth found himself with company at the top of the leaderboard when Poulter eagled the same hole.
Six-time European Tour winner Scott went back in front with a birdie at the seventh after hitting his approach to four feet, but there was a decisive swing at the tenth as Poulter went ahead for the first time.
The Ryder Cup star sunk a 20 foot birdie putt, while Scott missed his par effort from five feet.
Poulter, as so often is the case, produced a masterclass in clutch putts, but there was nothing he could do to rescue par when he mis-cued his tee shot at the par three 14th.
And Scott regained the outright lead when he drained a 12 footer at the 16th for birdie.
The former World Number Three could have held an even bigger advantage - at the par five last Poulter caught a flyer with his approach and was left with a near-impossible downhill birdie putt from the back of the green, while Scott's magnificent approach stopped five feet from the pin.
But the Australian misread the line, and Poulter once again bravely holed from a similar distance to save par and tee up an enthralling final day.
"At the 18th, I just over-read the putt a little bit but the course played hard on the back nine and it was hard to get it close, so I was happy to shoot par on the back nine," said Scott.
"I'd love to go out tomorrow and play really solid and whatever happens, happens. If I play solid I think I can get it done but if it's not enough then I will have to come back and try again next year."
Poulter added: "Hopefully I can go out there and play just as well and roll a few more putts in and who knows - I might just get my hands on the trophy again.
"We are mates off the golf course, I have known Adam for about 12 years. You get 40 or 50 seconds to stand over your shot, concentrate, and pull the trigger. Obviously you have time to relax between shots and Adam is a great and nice guy to talk to."
It is far from a two-horse race, however, with Kang's masterful approach to within three feet on the 18th highlighting the 27 year old's talent in a 67 that included eight birdies.
And US Open Championship winner Graeme McDowell is only two off the pace after a round of 68 that included a 50 foot birdie putt on the 14th.
The Northern Irishman also has the added incentive of trying to catch Race to Dubai leader Martin Kaymer, with the German tied for 14th on seven under.
"It's important that I focus on my own game as there's nothing I can do about Kaymer," said McDowell. "It's not rugby and I can't go out there and tackle him - all I can do is to concentrate on my own ball.
"I've got a big day tomorrow and it's a big day for The Race to Dubai. I've got to stay focused and play my game."
Dane Anders Hansen produced a best-of-the-day 65 to hold fifth on 11 under, one shot ahead of Wales' Jamie Donaldson.