Thailand's Pornanong Phatlum shot a 6-under round of 66 to take a one shot lead over South Korea's Amy Yang after the first round of the Lorena Ochoa Invitational in Guadalajara, Mexico.
Top-ranked Inbee Park from South Korea was two shots off the pace after posting an opening-round score of 68 at the Guadalajara Country Club. She is in a group of three golfers at 4-under that includes Sweden's Anna Nordqvist and South Korea's So Yeon Ryu.
Another shot back is American Michelle Wie and South Korea's Jenny Shin at 3-under. World No. 2 Suzann Pettersen from Sweden is among five golfers at 2-under, while third-ranked Stacy Lewis from the United States shot an even-par round of 72 on Thursday.
Phatlum is seeking her first career LPGA title. She got off to a hot start with birdies on each of the first three holes, and needed just 25 putts for the round.
"Well, today, my putting was very good," said Phatlum. "I had a complete game today."
Park remains in good contention as she chases her seventh victory of the season in the 36-player field.
"My ball striking was really good today," said Park. "I hardly missed any shots out there today, I didn't miss any fairways and probably missed only a couple greens but I was getting some muddy balls there and just didn't know where it was going to fly. I left a couple of putts out there today and I had a lot of opportunities. My ball striking was really good today though so hopefully I can keep it going the next three days."