Less than a week after shooting a career-worst 83 at the Women's PGA Championship, Kirk notched her personal-best score as she bagged 10 birdies on Thursday.

"Golf is funny," Kirk told reporters after establishing a one-shot first-round lead from South Korea's Sei Young Kim.

"When you've played it as long as I have professionally you realise some days will be good and some will be bad."

Back at the event where she broke a seven-year, 152 tournament victory drought last year, 36-year-old Kirk was on fire from the outset.

She opened with three successive birdies and bagging seven in her first nine after starting from the 10th hole at Thornberry Creek at Oneida in Wisconsin.

Her round was about as close to statistical perfection as it gets as she hit 14 of 14 fairways, hit 17 of 18 greens and needed just 25 putts.

Kirk lines up a putt on the second green during the Thornberry Creek LPGA Classic. PHOTO: Stacy Revere/Getty Images.

Canada's Brittany Marchand and American Megan Khang are tied third at eight under after a day of red-hot scoring.

Kirk drew on her experience at the inaugural tournament in 2017.

"Obviously, I know you can go low out there, so stepping onto the first tee, I said, 'Let's play aggressively and make as many birdies as possible.’

"Thankfully, it worked out. Having shot nine-under last year and I knew the conditions were going to be perfect this morning. ... I got off to a hot start and tried to keep the pedal down."

After missing the cut five times in her last six events and going without a top-10 finish since February, she's put herself back in contention.

"It is kind of generous off the tee (and) I've never been a very straight driver of the golf ball," she said with a laugh.

Minjee Lee is the next best Australian in a tie for 34th after a 68.