Justin Thomas made two eagles during a 9-under-par 63 round to open up a three-stroke lead after Thursday's opening round of the CJ Cup at Nine Bridges in Jeju, South Korea.
The reigning FedExCup champion also delivered seven birdies, including four straight on holes 14-17, and overcame two bogeys in his first trip around the course at the first official PGA Tour stop in South Korea.
Tony Finau, Russell Henley, Charles Howell III, Ollie Schniederjans and Venezuela's Jhonattan Vegas are another shot off the pace.
Thomas was surprised with his round because his day didn't begin well. He began play on the 10th hole and immediately bogeyed the par-4, 471-yard hole.
After making par at 11, the 2016-17 PGA Tour Player of the Year turned lava-hot with two eagles and four birdies during a seven-hole stretch.
"It was kind of a weird day," Thomas said. "It started off with a really, really bad bogey. And then I had a seven-hole stretch there where I basically kind of went unconscious. That was pretty much most of my round."
He was at 29 through his first nine holes, which led Thomas to feel a little disappointed that he didn't post a lower round than 63.
"On the last nine holes, I felt like, I had a really good opportunity to shoot something really, really low so that was a little bit of a bummer," he said. "Obviously, still pleased with the start. That birdie on the last hole was great. I felt like I could have played the last six holes a lot better than I did.
"If I would have parred my last hole, I would have had a pretty sour taste to my mouth walking off the golf course."
Australian and former world No.1 Jason Day was among a group of eight golfers who shot 4-under 68. Among the 10 golfers who carded a 69 were Patrick Perez and reigning Tour Rookie of the Year Xander Schauffele.
Seventeen Korean golfers are in the field with Whee Kim (68) and K.J. Choi (69) turning in the top first-round showings.