South Korea's Kim In-Kyung tied the tournament record with a stunning first round 63 at the LPGA Thailand on Thursday to take a three-stroke lead over world number one Yani Tseng.
The seventh-ranked Kim struck nine birdies in her nine-under-par round, three shots clear of Juli Inkster of the United States and Taiwan's Tseng after 18 holes at Siam Country Club's Old Course.
Kim started her day with a birdie at the par-five first hole and never looked back, nearly holing a birdie chip on 18 to set a new tournament record in the first USLPGA event of the season.
She joins Suzann Pettersen (2007), Stacy Prammanasudh (2009) and last year's champion Ai Miyazato in the record books with her bogey-free performance- matching her career-best showing.
Inkster, a 31-time Tour winner, overcame a rocky start to shoot 66. Looking for her first victory since 2006, she recovered from back-to-back bogeys at holes two and three.
Tseng, who has won all three of the events she has entered this season, including two on the Ladies European Tour, is in joint second place after also shooting a 66.
Scotland's Catriona Matthew (67) is a stroke further back, with Norway's Suzann Petterson shooting a 68.
A group of five players are on 69- South Korean pair Choi Na-Yeon and Yoo Sun-Young and Paula Creamer, Stacy Lewis and Michelle Wie, all from the United States.
"I started with a birdie and kept making birdies somehow. I didn't think about what I was going to do, I just played every shot," said Kim.
"My coach was caddying for me today and helped me a lot. We have been working on little changes, but the first event, you never know. You're excited and you want to see what's going on. I think it was a really good start. Couldn't be happier."
New world number one Tseng said she was pleased with her first round and that her stellar start to the year had boosted her confidence.
"Yeah, for sure it's a pretty good round for this course. It's playing longer this year. I hit lots of seven-iron, six-iron, five-iron, which is totally different from last year. I just didn't hit my irons as good, but I'm staying patient and I hope the next three days get better."
Inkster was pleased with her performance. "I hung in there and started hitting some really good irons and got some birdies. I didn't really get in too much trouble today. Hit my irons really good," she said.