Narin An of South Korea shot a flawless 8-under-par 64 to set the pace at the CME Group Tour Championship on Thursday in Naples, Fla.

A $4 million first prize is on the line at the LPGA's season finale at Tiburon Golf Club, where 60 players qualified based on the season-long Race to the CME Globe.

An has never won on the LPGA Tour, but she finished 29th in the points race thanks to four top-10 finishes. Now she is in great position to land a massive victory.

Angel Yin is alone in second, one stroke behind An, and Marina Alex and Allisen Corpuz are tied for third at 6 under. Lydia Ko of New Zealand is in striking distance of the lead after shooting a 5-under 67, part of a six-way tie for fifth.

An, 28, hit all 14 fairways in regulation and needed just 23 putts to get around the course. She carded four birdies on each nine without a bogey.

Though a $4 million paycheck is enticing, she said her attitude this week is that a tournament is a tournament.

"I think that mindset is good for make the focus during my play," An said.

Yin, 26, was 2 over through four holes before turning things around. She got into red figures with three birdies before the end of the front nine, and she poured in four birdies between Nos. 10 and 14.

Then, at the par-5 17th, she punctuated her day with an eagle 3.

"Started out a little bit rocky just because I was trying to adjust to the golf course," the Los Angeles native said. "Golf course is playing quite difficult with the early winds this morning, which I really like and I enjoy, because it's our last tournament and it's a huge purse, bigger than a major. Doesn't have a title of a major, but I think it deserves every bit of difficulty it brings to closing the season out."

Alex, 34, also made a jump by eagling the 17th, but not the way she planned it. After a second shot she was unhappy with, she chipped in on her third.

"(On 17 she was) just like classically in the worst place I could have been, left and slightly long of that particular pin," the two-time winner from New Jersey said. "... I thought I hit a nice chip. I was expecting it to be, I don't know, 10 to 15 feet, which was what I was going to be happy with trying to convert, and hit the pin and went in.

"Just you need some good breaks. Occasionally that kind of stuff happens."

Former U.S. Women's Open champ Corpuz had a bogey-free day, while Ko carded six birdies and one bogey.

Ko is trying to polish off perhaps the best year of her career after she already collected an Olympic gold medal and the Women's Open title. She also qualified for the LPGA Hall of Fame and was inducted last month.

"I think this is the type of golf course where it's not like one fights into this type of golf course," Ko said. "We've seen various of winners here, from longer hitters to people that hit it really straight and et cetera.

"... I think it's going to be exciting. It's always an exciting finish here. Hopefully, I'll be able to hit and play my fair share of good shots and be in contention and finish the season officially on a high."

World No. 1 Nelly Korda, who finished No. 1 in the points race, shot a pedestrian even-par 72 and is tied for 44th. Lexi Thompson, who's wrapping up her final full-time season on tour, is tied for 50th at 1-over 73.

--Field Level Media