The Kiwi number one now shares the lead with America's Lexi Thompson at -15, in search of her first title in more than 12 months. She relished having a big lead after finishing runner-up five times this year, three times in playoff losses.
Kung is well within striking distance, just a stroke behind the leaders after a round that featured nine birdies and one bogey.
"I know I've still got a whole, full 18 holes tomorrow to go, but I think really the key was that I've just kind of enjoyed being in this position and being able to hit some good shots and give myself some good looks at birdie", Ko said.
Chasing a first win in more than a year, Ko's cautiously pleased with her round.
With the Red Bull logo on her hat matching the logo on the Speedway's Corvette Stingray pace auto, Lexi birdied the reachable par-4 18th to capture her ninth career LPGA victory and don the champion's wreath bestowed upon all winners at the Indianapolis Motor Speedway.
Gal, like Thompson, started her morning round on the back nine that features four holes inside the Indianapolis Motor Speedway. She closed with her sixth birdie of the round.
As for Ko, while Saturday may not have ended in victory, it was certainly a breakthrough week for the young New Zealander. It's a great mixture of holes, and that's why when you see the leaderboard, there's not just one type of player.
"I'm all about driving fast", said Thompson. "After a year ago, I felt like I could improve ball-striking". However, she has not finished higher than 10th in an event since then, and she missed the cut in two of her last three tournaments.
"I just wasn't putting as well as I did the last few days, and that makes a huge difference", Ko said.
"It's so different than every other golf course that we get to play", Henderson said.