Ai Miyazato fired a 5-under 67 to take the lead after the first round of the Honda LPGA Thailand on Thursday.
Playing in her first event of the season, Miyazato reeled off five birdies in a flawless round at Siam Country Club to take a one-shot lead over South Korean trio Choi Na Yeon, Pak Se Ri and Amy Yang, Australia's Karrie Webb and Anna Nordqvist of Sweden.
"I have made a great result in making no bogeys. I'm glad I could finish the day on a high note," said Miyazato. "It's been a long, hot day."
Former world No. 1 Miyazato won this tournament two years ago, following up with victory at the HSBC Women's Championships one week later to become the first Japanese player to win back-to-back titles on the LPGA Tour.
World No. 1 and defending champion Yani Tseng of Thailand got off to a lackluster start with a 73.
Elsewhere for Japan, Mika Miyazato, no relation to Ai, was tied for 26th after shooting an even-par 72, while Momoko Ueda and Shinobu Moromizato struggled with 74s.