Ko, with Australian super-caddie Dean Herden on her bag, outplayed her more credentialed rivals, the closest of whom are winners of the US Women's Open in two of the last three years.
The secret is however to outplay them again tomorrow which, if she is able to do, will assure her of a card to play the LPGA Tour from this point on.
The 22 year old has been a prolific winner of titles and money on the various ladies tours in South Korea including nine on the KLPGA Tour and so winning tomorrow would not be a new experience for her but at this level it certainly would.
It would also open the door to the LPGA Tour which she has yet to play as a member although clearly she has the game to eventually succeed wherever she plays.
Ko is in her 4th season as a professional and in 2016 was the Player of the Year on the KLPGA Tour and became just the third player ever to earn more then US$ 1 million in a season there.
Herden, who now lives in Korea, has played a role in the development of several young Korean golf stars including So Yeon Ryu, Jiyai Shin, In Gee Chun and now Ko amongst others. In Ko he appears to have assisted in unearthing another emerging talent irrespective of what happens tomorrow.
A win by Ko tomorrow would see Herden take his wins as a caddie past the 50 mark.
Lizette Salas is three shots from the lead and alone in 4th position while Australian Minjee Lee is not without her chance at 11 under, a scores she shares with Marina Alex and long hitting Angel Yin.
Su Oh is 46th, Sarah Jane Smith 59th and Katherine Kirk 72nd.
HANNAH GREEN 2ND ON SYMETRA TOUR MONEY LIST
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.