KUALA LUMPUR, October 9, 2014 (AFP) - Lewis, who went bogey-free, added her sixth birdie of the day on the 16th hole to edge in front of a South Korean pack at the challenging Kuala Lumpur Golf and Country Club.
South Koreans Na Yeon Choi, Hee Young Park, Eun-Hee Ji and So Yeon Ryu were tied on 66, just a stroke back.
Several other golfers were a further shot behind, including Mi Hyang Lee of South Korea and last year's runner-up Shanshan Feng of China.
The $2 million tournament is part of a several-event swing through Asia by the US LPGA.
Last month, Lewis finished second to South Korea's Hur Mi-Jung in the LPGA Yokohama Tire Classic in Japan, and performed strongly last week at the Reignwood LPGA Classic in Beijing.
"Yeah, another week I got off to a good start again," Lewis said after her round Thursday.
"It was kind of one of those rounds that early it was actually kind of shaky and I had to make a few par putts on the first three holes, but really just kind of hung in there and gave myself a lot of birdie looks and was fortunate to make a few."
Last year's champion Lexi Thompson was 6 strokes off the pace after the American shot an opening-round 71.
Rising youngster Lydia Ko of New Zealand, who is now number-three in the world but is gunning for Lewis's top ranking, was in the hunt after the 17-year-old finished with a 69.
Scores in brief:
65 - Stacy Lewis (USA)
66 - Na Yeon Choi (KOR), Hee Young Park (KOR), Eun-Hee Ji (KOR), So Yeon Ryu (KOR)
67 - Shanshan Feng (CHN), Mi Hyang Lee (KOR), Jenny Shin (KOR), Amy Yang (KOR), Pornanong Phatlum (THA)