KUALA LUMPUR, 7 Feb 2015 (AFP) - Westwood, who held a share of the lead at the end of each of the first two days, remained in contention three strokes back with a 69 for the day.
But the Englishman, who is notably comfortable with the Kuala Lumpur Golf and Country Club's undulating fairways, has snared fewer birdies each day as others seem to be figuring the course out -- including Wiesberger.
On a day where temperatures climbed to 33 degrees centigrade (91 fahrenheit), the Austrian started hot and cooled only slightly on his way to 10 birdies and sole first place at 17-under-par for the tournament.
"It was a great day for me. This is my European Tour record. I've never shot a 63," he said.
"But I had a fast start today and anybody can do that tomorrow. If I keep playing like this then I have a good chance to take this home."
Second-round co-leader Alejandro Canizares was two strokes behind Wiesberger at 15-under for the event after shooting a 68 that included an eagle -- a 110-yard approach that skipped into the hole on the par-four 16th.
Westwood was tied for third along with his fellow Englishman Paul Waring at 14-under.
"I didn't play particularly well today, so I was pleased to shoot 69, which keeps me in the hunt," said Westwood, who won last year by seven strokes and also took the title in 1997.
It would have been worse for Westwood, but he managed to convert two birdies on his last two holes.
"If I didn't make them I'm looking at probably being five shots back, so it was nice to finish with a bit of momentum," he said.
India's Anirban Lahiri matched Wiesberger's 10 birdies, posting a bogey-free 62, the lowest score of the tournament so far, to sit five strokes off the top.
One shot behind Lahiri was Paul Peterson of the United States, who carded a 64.
Former Major winner Graeme McDowell's hopes appeared dead following an even-par effort that left him 12 shots off Wiesberger's pace.
Leading third-round scores on Saturday in the $3 million Malaysian Open at Kuala Lumpur Golf and Country Club (par 72):
199 - Bernd Wiesberger (AUT) 70-66-63
201 - Alejandro Canizares (ESP) 68-65-68
202 - Paul Waring (ENG) 69-68-65, Lee Westwood (ENG) 66-67-69
204 - Anirban Lahiri (IND) 70-72-62
205 - Paul Peterson (USA) 72-69-64
206 - Richard T. Lee (CAN) 69-69-68
207 - Jake Higginbottom (AUS) 69-71-67, Alvaro Quiros (ESP) 70-70-67
208 - Gregory Bourdy (FRA) 70-70-68
209 - Pablo Larrazabal (ESP) 73-69-67, Peter Uihlein (USA) 72-72-65
210 - Wang Jeung-hun (KOR) 77-66-67, Danny Chia (MAS) 67-74-69, Kang Sung-hoon (KOR) 67-74-69, Marc Warren (SCO) 70-71-69, Prom Meesawat (THA) 68-72-70
211 - S.S.P Chowrasia (IND) 76-67-68, Johan Carlsson (SWE) 74-69-68, Nicolas Colsaerts (BEL) 70-74-67, Scott Hend (AUS) 73-72-66, Graeme McDowell (NIR) 66-73-72, Richard Bland (ENG) 68-70-73