Miami - South Korea's An Byeong-hun, chasing a first PGA Tour title, fired a five-under-par 65 on Friday to take a one-shot lead into the weekend at the Wyndham Championship.
An, who shared the overnight lead with compatriot Im Sung-jae in the final regular-season event prior to the US tour's playoffs, had five birdies without a bogey at Sedgefield Country Club in Greensboro, North Carolina, for a 13-under-par total of 127.
He was one stroke in front of American Brice Garnett, who carded a six-under 64 for 128, with half a dozen players sharing third on 129.
"I had to grind it out to make it bogey-free today," said An, who teed off on 10 and birdied 14 and 15.
He launched a run of three straight birdies with a near-ace at the par-three third, where he stuck his tee shot a foot from the pin.
He rolled in a 30-foot birdie putt at the fourth and two-putted for birdie from 32 feet at the fifth to reach 13-under and salvaged par from the right rough at the ninth to stay there.
"It was slightly worse than yesterday," said the 27-year-old from Seoul, who has twice lost in playoffs on the PGA Tour - at the 2016 Zurich Classic and at Memorial last year.
"I didn't have as many birdie chances as yesterday, but I made some long putts and made all the birdies at the par-fives, I think that was the key today."
Garnett had six birdies without a bogey to climb the leaderboard, draining a 36-foot putt at the 18th - his ninth hole of the day.
"The putter's been working nice for about the last eight weeks or so," he said. "I don't think the ball-striking's been quite up to par, but sometimes if you wiggle the putts in it doesn't really matter."
Im followed up a first-round 62 with a 67 to join the group on 129.
That also included Canadian Adam Svensson, who had nine birdies in a nine-under-par 61.
"It was pretty exciting," said Svensson, who had seven birdies on the front nine and two coming in.
"Coming down the stretch I was a little nervous," he admitted. "I was actually looking at the scorecard again, I was like, is this a par-70? I have a chance to shoot 59 - it kind of started to get in my head a little bit."
Even so, Svensson managed to avoid any big mistakes to join Im, Patton Kizzire, Josh Teater, Webb Simpson and fellow Canadian Mackenzie Hughes on 129.
Svensson, 25, likely needs at least a top-three finish if he's to break into the top 125 points and maintain his tour card.
Although he has struggled plenty in his rookie season, he's hoping he can draw on his experience at the Sony Open in January, when he opened with a 61 before fading to finish tied for 43rd.
"I just played too aggressive trying to get out front," he said of following up his low round there. "Tomorrow I'm just going to play my normal game."
Leading second-round scores at the PGA Tour's Wyndham Championship on Friday at Sedgefield Country Club in Greensboro, North Carolina (par 70; USA unless stated)
127 - An Byeong-hun (KOR) 62-65
128 - Brice Garnett 64-64
129 - Im Sung-jae (KOR) 62-67, Patton Kizzire 65-64, Adam Svensson (CAN) 68-61, Josh Teater 64-65, Webb Simpson 64-65, Mackenzie Hughes (CAN) 63-66
130 - Ryan Armour 64-66, Paul Casey (ENG) 65-65, J.T. Poston 65-65
131 - Charles Howell 66-65, Jordan Spieth 64-67, Bud Cauley 65-66, Kim Si-woo (KOR) 66-65, Rory Sabbatini (SVK) 63-68, Fabian Gomez (ARG) 67-64, Sepp Straka 65-66
132 - Shawn Stefani 66-66, Brian Stuard 66-66, Matthew Wolff 65-67, Johnson Wagner 63-69, Brian Harman 67-65, Harold Varner 66-66, Brandon Harkins 68-64, Viktor Hovland (NOR) 66-66