Creamer, who finished third last week at the Honda LPGA Thailand after losing the final-round lead, battled through an apparent bout of food poisoning to join compatriot Jane Park and Brazils Angela Park atop the leaderboard at the Tanah Merah Country Club course.
For some reason I putt better when Im sick, Creamer said. At the beginning, I was very sick, very nauseous. It must have been something I ate.
Play was delayed for 52 minutes in the afternoon because of lightning.
Japans Ai Miyazato and South Koreas Seon Hwa Lee finished the round one shot back of the leaders at 4-under 68.
World No. 1 Lorena Ochoa of Mexico, the defending champion, tied four other players with a 69.
Anytime you start under par, its always good, Ochoa said. I think I need to be a little more aggressive.
Second-ranked Yani Tseng of Taiwan and world No. 4 Suzann Pettersen of Norway each shot an even-par 72.
Fifteen-year-old Singapore native Joey Poh, the only amateur in the field, had a 6-over 78.