After experiencing the highest of highs and then some crushing lows in a rollercoaster second round, Su Oh still finds herself in the mix at the LPGA's Mediheal Championship.

The Australian shot a two-under 70 at Lake Merced Golf Club on Friday to be three-under for the tournament, four adrift of leader Danielle Kang (66).

But her scorecard didn't tell the full story of the world's leading amateur in 2013.

Oh got off to a dream start when she followed her birdie on the second with a hole-in-one on the third. She made further birdies on the eighth and 10th before coming unstuck.

Her horror run began on the 11th when she went double-bogey, bogey, bogey - dropping four shots in three holes.

She recovered to make birdie on the 17th and par on the last to close an eventful round to say the least, tied in ninth position.

Kang enjoyed a birdie blitz en route to a blistering 66 - the low round of the day.

The 28-year-old began quietly with just one birdie, on the par-3 third hole, and six pars through her first seven holes.

She finished the front nine with consecutive birdies, starting a stretch of six in her final 11 holes, to grab the midway lead by one from Lauren Kim (69) and first-round leader Leona Maguire (73).

"I actually played really well from the beginning, better than I did on the back nine," Kang said afterward. "I just couldn't quite get the ball to the hole, but I knew I was putting well.

"The greens are slick and fast, a little scary, a little bumpy. You have to trust your lines, and that's what I have been doing. Just kept putting the way I did and started dropping on the back nine."

Min Lee of Taiwan is fourth after shooting a 69 that included eight birdies and five bogeys.

Australian Minjee Lee improved on her opening 73 with a 69 to be two under for the tournament.

Lee is tied 20th, while 2019 Women's PGA champion Hannah Green is a shot behind after her 71.