Defending champion Na Yeon Choi and Karrie Webb both shot a 6-under 65 on Thursday to share the lead after one round of the Sime Darby LPGA Malaysia.
Choi, who won the U.S. Women's Open for her first major title in July, fired six birdies and endured a lightning delay during her bogey-free opening round at Kuala Lumpur Golf and Country Club.
"The main thing is I know the course very well and I know I have ability to play well because I did last year," said Choi. "So I just try to think positively. I have lot of pressure, but I try to thrive off the pressure."
Webb, a 37-time LPGA Tour winner, also finished without a bogey on Thursday to secure a share of the lead.
Min Lee, Mika Miyazato and Sun Young Yoo are tied for third place at 5-under, while Hee Young Park and Hee-Won Han both shot 67 to share sixth.
"I hit my second shots very well on the back nine," said Miyazato, who recorded three top-10 finishes in majors this year. "The front nine was ok. I think my concentration was a lot better. I'm looking to really keep my rhythm this week."
World No. 1 Yani Tseng, who finished one stroke back of Choi at this event in 2011, is tied for 66th place after recording three double-bogeys during an opening-round 78.
Top American and World No. 2 Stacy Lewis fared better on Thursday with a 1- under 70 and resides in a large group tied for 24th.
Tseng and Lewis are the only players with three tour wins in 2012.
Third-ranked Jiyai Shin, who is attempting to win her third consecutive event, shot par. The South Korean captured the Ricoh Women's British Open and the Kingsmill Championship in her previous two tour appearances.
Also on Thursday, Michelle Wie opened with a 4-over 75 to sit in a group tied for 62nd place.
Choi was 4-under through eight holes and recorded another birdie on the 12th before lightning forced her to halt. After the delay, Choi birdied No. 14 to get to 6-under, then closed with four straight pars for her opening-round 65.
"I feel great," said Choi. "I'm very happy. We still have three more rounds, but I have a lot of confidence, especially with this golf course."
The Sime Darby LPGA Malaysia is the first of four events in the tour's Asian swing, which also features stops in South Korea, Taiwan and Japan.
NOTES: Choi is seeking her second tour win of the year...Seven players are tied for eighth place at 3-under...The top 10 players in the world are in the field.