JEJU, South Korea (AFP) - Justin Thomas battled to a two-under par 70 in brutal winds at the CJ Cup on Saturday and thought he played better than when shooting 63 two days earlier.
It took Thomas into a share of the lead with fellow American Scott Brown on nine-under 207, two strokes clear of India's Anirban Lahiri and Australia's Marc Leishman.
"I know for a fact that I played better today than I did on Thursday when I shot nine-under," said the world number four after only 10 players in the elite 78-man field broke par.
"It is so hard out here, I've never played a place where the wind swirls as much as it does here. It was insane."
The US PGA Tour's first event in South Korea has taken the players to the slopes of the 1,950-metre (6,400-foot) Halla Mountain, an extinct volcano on Jeju that is South Korea's highest peak.
The spectacular Nine Bridges club has a reputation as a windy venue, but Thursday's flat calm saw a flurry of low scores headed by Thomas's 63.
On Friday and Saturday the course bit back with a vengeance and Thomas remains on the same nine-under mark relative to par.
"The hardest thing is the putting," Thomas said. "We'll hit some putts that look pretty stupid out there and the viewers at home don't understand. You have to be out here and close to know why that's happening."
Brown shot a one-under par 71 that felt much lower, he said.
"When it's like this, I mean hitting a sand wedge into a green is hard," said Brown, who had his best season on the PGA Tour last year when he finished 55th in the FedEx Cup.
Lahiri is back on familiar turf having played seven years in the Asian Tour and used his experience to card one of the rounds of the day, a three-under 69 that catapulted him from 15th to joint third.
Lahiri had looked like carding the only bogey-free round of the day until he dropped a shot at the 16th. "I'm a little disappointed honestly with my back nine. I felt like I missed a lot of putts."
Lahiri lost to Thomas in a play-off at the CIMB Classic in Malaysia a year ago, but that would have no bearing Sunday he said.
"This golf course is not playing anything like TPC Kuala Lumpur, I promise you." said Lahiri. "Whoever I play with tomorrow I'm happy I have given myself a chance."
The best round was a 67 containing seven birdies and two bogeys by local hero An Byeong-Hun.
He started on the 10th earlier than the leaders and took advantage of calmer conditions on the back nine to bag five birdies before the turn to get to level par for the tournament.
That gave him a share of eighth place with overnight leader Luke List, who fell away with a 76.
Whee Kim continues to be the best of the 17 Koreans in the field and will start Sunday three off the leaders after a patient level-par 72.
"The wind blew everywhere. I think I did pretty good considering," said the in-form Kim, fresh off winning a BMW 7 series for a hole-in-one in Malaysia last week
"I think I'm in a really good position for Sunday. If it blows again I just need to stay patient and keep it low."
He is in a three-way tie for fifth on six-under for the tournament with Australia's Cameron Smith, who had a 73 and former US Open Champion Lucas Glover, who returned a 74.