The South Korean amateur was three shots clear after opening with four birdies in her first five holes before stumbling with a bogey to hit the turn at Kingston Heath Golf Club at 10 under on Friday.
Yang's closest pursuer was 20-year-old Queenslander Justice Bosio, who earlier snatched the clubhouse lead from world No.6 Hannah Green with a birdie at her last hole in a fine second-round 69 at Victoria.
Bosio is contesting only her fourth professional tournament after a distinguished amateur career, but now stands two rounds away from potentially taking the Australian Open trophy back to Caboolture.
Young Queenslander Justice Bosio has her sights set on the Australian Open trophy. (Con Chronis/AAP PHOTOS)
"Pretty surprising. I know that my game is there and I have been working really hard lately but, yeah, it's just been really cool to see the hard work is paying off the last two days," the 2023 Karrie Webb Scholarship winner told AAP.
"I've still got some good rounds out there, but still lots of work to go."
Bosio could even wind up playing with Green on Saturday.
"That'd be really cool," she said.
"I'll be very nervous, but I'm sure she's really nice. I've never played with her before, but it'll be cool to watch her game and whoever else we might end up playing with."
Green finished with a flurry herself with two birdies in a 71 at Victoria to join her best mate and first-round co-leader Su Oh at seven under for the championship.
"It was nice to at least finish with two par-5s and be able to get two birdies to finish on a positive note and good momentum going into the weekend," Green said.
"I've put myself in a good position for the weekend, so hopefully Kingston Heath, we don't get too much rain.
"Honestly I've heard mixed forecasts. I've heard there's going to be a little bit of rain, I've heard a lot of rain, so it really depends on that.
"But I think Kingston is already soft and so that will help us women to make lots of birdies. You still have to go low, so we'll see what happens with the rain."
Defending champion Ashleigh Buhai bounced back with a 68 in the second round of the Australian Open. (Con Chronis/AAP PHOTOS)
Two-time defending champion Ashleigh Buhai was the morning's big mover on Friday.
Playing with Green, the South African carded a 68 to surge into the top 10 at four under.
Buhai had fallen nine shots off the pace on Thursday when she slumped to three over, but clawed her way back to even par before producing a bogey-free second round.Â
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