Kim, who started the day with a five-shot advantage on the field, bounced through an even-par round of 70 that featured three birdies and three bogeys. She finished at 14-under-par 266 to set the 72-hole scoring record for the tournament.
American Ally McDonald finished second at 11-under after shooting 68 on Sunday.
“Yeah, just if I play same as last three days, yeah, I expect for sure [to win],” said Kim, who earned her second win of the season and her 12th career LPGA victory.
“But Ally played quite. … When I to three-shot lead I was like, ‘Oh, my God, she can’t be like chase me.’ I was like, ‘OK, Sei Young, focus, keep going.’ Yeah.”
Kim’s round was marked by solid driving and putting: She hit 12 of 14 fairways (12 of 18 greens) and took just 30 putts on Sunday. The 27-year-old won the KPMG Women’s PGA Championship in early October in her last start.
McDonald, who won her first LPGA Tour title last month at the LPGA Drive-On Championship, played her ninth straight round under par dating back to the final round of the KPMG Women’s PGA Championship. She bounced back from a bogey at No. 3 to notch three birdies over her next four holes and put a little pressure on Kim, but an even-par back nine left her short of any trophy aspirations.
“Once we got to a point, I just tried to take Sei Young out of it and play like a little tournament within the rest of the field,” McDonald said. “She got out to such a big lead on the last few holes. I’m really happy with how I played. I hung in there, made some great up and downs. …
“So I’m really pleased. Obviously following a win to get another second and be in contention, that’s all I can ask for.”
Rounding out the top five were United Kingdom’s Stephanie Meadow (69), who finished alone in third place at 9-under. Finishing tied for fourth at 8-under were New Zealand’s Lydia Ko (69) and American Austin Ernst (68).
In a four-way tied for sixth place were a trio of Americans including Jessica Korda (64), Angela Stanford (65) and Jennifer Song (65), as well as Canadian Brooke Henderson (69).
Korda’s bogey-free 64 was low round for the day.
“I … definitely minimized some of the mistakes; less wind today, which I felt like it maybe played a bit easier,” said Korda, a five-time LPGA winner.
“I just gave myself better numbers, and with the wind it’s kind of tough to get yourself exactly the numbers that you like. But we had a lot of the same numbers today, so I was able to capitalize and I made some really long putts, too, which obviously always helps.”