South Africa's former British Open winner carded a three-under-par 70 at The Lakes on Friday to climb above first-round pacesetters Jenny Shin of the USA and Sydney teenage prodigy Rachel Lee.
Buhai is seven under at the halfway point, one stroke ahead of Shin, who posted an even-par 73 at The Lakes, and also Lee, who was playing in the afternoon at The Australian.
After opening with a four-under 69 at The Australian on Thursday, Buhai made a fast start to her second round with three consecutive birdies from the second hole.
She reached the turn in eight under for the tournament but dropped a shot with two bogeys and a lone birdie on the back nine.
The 34-year-old is nevertheless delighted to be perched on top.
"It's a really good position any time you're in there near the top going into the weekend," Buhai said.
"I'm feeling good so far this week. I've taken it easy. I think it also helps."
Buhai, though, insists it's too early be thinking about going back-to-back in Australia.
"I've just got to focus on doing my steps and process. That's all I can control," she said.
"The minute you start thinking about the outcome, that's when trouble happens.
"My goal this week was to not have very high expectations and have fun and that's what I've done the last two days."
Teenager Justice Bosio in early morning round two action at the Australian Open in Sydney. (Dan Himbrechts/AAP PHOTOS)
Queensland teenage amateurs Justice Bosio and Sarah Hammett, both in the Golf Australia high-performance programs, were other morning movers.
Bosio, 19, surged into a tie for fifth with a four-under 69 at The Lakes, while 16-year-old Hammett is one stroke back after a one-under 71 at The Australian.
Runner-up in the Australian amateur championship the past two years, Bosio mixed five birdies with just one bogey to be at four under at the halfway stage of the Open.
But more fancied compatriots Grace Kim and Hannah Green could only manage 73s at The Lakes.
Kim remains at two under for the championship, and five strokes adrift of Buhai, with Green level with the card.
Pre-tournament favourite Minjee Lee, at three under, and Steph Kyriacou, at four under, were playing in the feature afternoon group at The Australian.
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