Thorbjorn Olesen shot a five-under-par 67 on Saturday to take a three-shot lead into the last round of the Perth International.
The Dane, who is looking to secure his second European Tour victory, managed six birdies and just a single bogey to hit 16-under par at Lake Karrinyup.
The 24-year-old now has a three-stroke cushion over nearest challenger Shiwan Kim of Korea [69], who led overnight, and also sits a shot ahead of Englishman James Morrison [69] in third.
The biggest mover of the third round was American Peter Uihlein, who posted a 65 to climb into fourth on his own at 11-under.
Richard Green and Scotland's David Drysdale share fifth place, but it was a day to forget for his compatriot Peter Whiteford, who slumped to a three-over 75 as his hopes of retaining his card for next season took a blow.
