Ai Miyazato shot a 5-under 67 Thursday to take a one-stroke lead after the first round of the LPGA Thailand.
The 2010 champion from Japan opened with a birdie and went on to sink four more on a warm and humid day at the Old Course at Siam Country Club.
Five others were one shot behind, including third-ranked Na Yeon Choi. The others are Se Ri Pak, Amy Yang, Anna Nordqvist and Karrie Webb.
Webb made a run on the back nine, sinking four birdie putts.
Numa Kulyanamitta (69) is tied for seventh along with Christel Boeljon, while Stacy Lewis (70) dropped off the top of the leaderboard with a triple-bogey on the last hole.