He missed a birdie putt in front of the 19th hole VIP hospitality to seal the mark on his own.
Koh’s resolve was as hard as the schist surrounding him throughout, trumping the earlier foray of Australian James Marchesani who carded a six-under par 65 on the same course to sit three strokes back.
“My caddie and I just picked some good options on the safe sides of greens, and then I putted great, which gets you to the top of the leaderboard in conditions like this.
“That part of my game has been going well for what feel like six to eight months so, if you’re giving yourself a few looks at birdies, a lot of them will go in.”
His compatriot Daniel Nesbit set the tournament record of 27-under par in 2018 when the event was co-hosted with The Hills.
Those performances camouflaged a strong outing from the locals, nine of whom will play the third and fourth rounds.
Josh Geary and Michael Hendry led the way, matching each other again with five-under rounds of 66 on the Coronet layout to sit at 10-under.
“I had a slow start with a couple of bad lies,” Geary confessed.
“Then I had a hot streak for seven or eight holes which enabled me to stay in touch.
“I’ve got a few rellies, uncles and aunties, who are pretty die-hard fans out to see every shot. A couple of them are injured, but they’re still out in the cart watching.”
Hendry lamented inconsistencies.
“The first round was really solid from tee to green, quite clinical, but I didn’t get it done on the greens.
“Today was the exact opposite. I definitely putted better, but played worse elsewhere.”
Daniel Hillier was a stroke back after a round which included seven birdies and a bogey.
What was his highlight?
“The way I kept my cool. I was frustrated through the middle, but knew there were some chances coming in.
“Some putts slipped by, but I held it together to finish with a couple of birdies.
“The greens are pure so some decent putts will be holed across the weekend. Hopefully I’m one of the guys to do that.”
Another New Zealand highlight was Steven Alker on the Coronet course sinking a 10-foot birdie putt to finish and clamber inside the cut.
The crowd in the amphitheatre surrounding the Millbrook club house gave him a rousing roar to celebrate a successful homecoming.
The other New Zealanders to make the weekend were Ben Campbell, Denzel Ieremia, James Tauariki, Mark Brown and Sam Jones.
First-round leader Harrison Crowe has slipped down the leaderboard into a tie for 12th at nine-under after shooting even par.
A highlight on the pro-am front was former Australian cricket captain Ricky Ponting securing an eagle on the Remarkables’ par-4 seventh hole, producing a straight drive down the ground to the green from 276 metres.
