Kim, who eclipsed the previous course record of 66 shot by Australian Nadina Taylor at an amateur event in 2000, had just 26 putts in what she described as "one of those days".
"I was just picking my line and rolling them in, let the ball do the rest," the 22-year-old said. "I felt really confident ... I was pretty ready for it so (I am) not surprised."
As play continued in the opening round, Kim was three shots clear of American Casey Grice, with Japan's Jenny Shin, Thailand's PK Kongkraphan and South Korean amateur Hye Jin Choi in the clubhouse at five-under.
Australians Minjee Lee and Su Oh carded three-under rounds while world No.1 Lydia Ko shot a two-under 70.
Ko, seven strokes back of Kim, was satisfied with her opening round's work.
"I'll take it," Ko said. "I hit two really loose shots where it was hard to put myself in position the next time but overall I played pretty solid.
"Not many putts dropped ... they were hitting the edges (but) I think I was putting a good stroke on it and that's all you can do."
-AAP