The 16-year-old Ko turned pro late last year. She won the Canadian Women's Open the last two years as an amateur and closed last season with a victory in a non-tour event in Taiwan in her second pro start.
Ranked No. 4 in the world, the South Korean-born New Zealander had six birdies and a bogey on Atlantis Resort's Ocean Club course.
Lee, from South Korea, eagled the par-4 13th and had four birdies and a bogey.
Jaye Marie Green had a 71. The 19-year-old Green won the LPGA qualifying tournament by 10 strokes last month, finishing the 90-hole event at a record 29 under.
Michelle Wie shot 72.
Defending champion Ilhee Lee opened with a 74. Last May, the inaugural event was reduced to three 12-hole rounds because of flooding.