Defending champion Nicolas Colsaerts of Belgium was lying in second place after birdying the last hole for a round of 66, and Paraguay's Fabrizio Zanotti was another shot down in third.
Meanwhile, Sweden's Alexander Noren took advantage of the favourable conditions to shoot a new course record with a round of nine-under par 63 at the $3 million event co-sanctioned by OneAsia and the European Tour.
That put him on an overall total of 203, five shots behind the leader and with a share of fourth place.
Grace, 24, has already won twice this season, at the Joburg Open and at the Volvo Champions of Golf tournament in his native South Africa.
"It is hard to believe that I am going for third title of the season," he said, according to a OneAsia press press release. "I don't think may people expected me to do that and I probably didn't myself."
"I knew that one win was round the corner but to win two back-to-back was amazing. Now I am looking good for the third at the moment but I have to try and not think about that too much tomorrow and go out there and play the way I have been all week."
Noren's course record included 10 birdies and a bogey. He attributed his new found form to a change in his practice routine.
"I am now trying to concentrate on hitting less shots but concentrating a lot more and trying to produce real quality all the time," he said.
"You look at the guys who are the best in the world and they seem to do that. I haven't done that in the past but I am feeling the benefits of it now."
England's Ian Poulter, at 25 the top ranked player in the field, shot a 70 for a total of 212, some 14 shots off the pace.
Leading scores after the third round (A denotes amateur):
198 - Branden Grace (RSA) 67-67-64
201 - Nicolas Colsaerts (BEL) 68-67-66
202 - Fabrizio Zanotti (PAR) 70-68-64
203 - Alexander Noren (SWE) 68-72-63, George Coetzee (RSA) 72-67-64, Ignacio Garrido (ESP) 67-69-67, Marcus Fraser (AUS) 67-69-67, Jean-Baptiste Gonnet (FRA) 66-67-70
Selected:
204 - Gary Boyd (ENG) 66-67-71
212 - Ian Poulter (ENG) 71-71-70, Colin Montgomerie (SCO) 68-72-72