Australia's world No.8 posted a flawless eight-under 64 to be tied with South African Ashleigh Buhai and South Korea's Jenny Shin at Seowon Hills CC on Thursday.
Two-time Women's Australian Open champion Buhai posted her score early but Green matched her tally of eight birdies with eight of her own after birdies at the last two holes late in the day.
Not to be outdone, Shin also came home strongly to join them atop the leaderboard as the trio took a one-shot lead from South Korea's Haeran Ryu on a low-scoring day.
The field is loaded with eight of the LPGA Tour's top 10 players. It also includes 17 of the 18 winners this season on the tour. About the only key player missing is American Kelly Korda who withdrew with a neck injury.
In her seventh year on the LPGA Tour, 27-year-old major winner Green is aiming for a fifth career LPGA title, having already won the HSBC Women's World Championship in February and the LA Championship in April.
It was a promising day for the Australian contingent with defending champion Minjee Lee and Grace Kim both posting 67s to be tied 11th.
Minjee Lee made a strong start in her tournament title defence. (AP PHOTO)
Lee is seeking an 11th career LPGA win and first since last year's triumph on the same course.
Hira Naveed shot a 70 while fellow Australian Gabriela Ruffels had a 72.
- with The AP
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