Pornanong Phatlum fired a six-under 67 on Sunday to earn a four-stroke victory at the Brasil Cup.
Phatlum had held a share of the first-round lead after carding a 66 on Saturday, then turned in a bogey-free round to secure the title of this two- day, unofficial event.
She drained five birdies on the front nine at Itanhanga Golf Club and cruised to the win on the back nine, finishing at 13-under par 133.
"I'm so excited today," Phatlum said. "I played really well today and I played on my game. I'm just very happy today."
Amy Hung fired a 65 to take second at minus-nine, while Chella Choi (67) and Paula Creamer (69) shared third at eight-under.
"I played really well today," Creamer said. "I had a lot of birdies, definitely enough birdies to win the golf tournament, but too many bogeys in two days."
Karine Icher, who shared first after Saturday, posted just a 73 for her second round and finished in a tie for fifth at seven-under.
Phatlum, 22, has never won on the LPGA Tour, but quickly separated herself from the field.
She began the day tied with Icher and one shot ahead of Katie Futcher, her two playing partners for Sunday's round.
Phatlum rolled in her first birdie at the par-five second hole, which Futcher also birdied to stay within a stroke. But Futcher fell down the leaderboard by following with three consecutive bogeys, and didn't make another birdie until the 11th hole.
Icher also struggled on the front nine, only to a lesser degree. She bogeyed the fifth and birdied the sixth to remain stuck at seven-under.
Phatlum, on the other hand, extended her advantage with a superb front nine. She birdied the fifth to get to nine-under, then made the turn at minus-12 by making birdies at seven, eight and nine.
Hung was the only player to shoot better than 67 on Sunday, but began the round too far back to gain significant ground on Phatlum.
The leader birdied the 11th, then parred out to clinch the victory.
NOTES: Phatlum collected $108,000 for the victory...Suzann Pettersen, the highest-ranked player in the field at world No. 3, carded a 73 and shared 10th place at five-under...Mariajo Uribe, the 2011 champion, shot a two-over 75 and finished at plus-two...The LPGA has next week off, then resumes play May 17 with the Sybase Match Play Championship. Pettersen beat Cristie Kerr 1-up last year.