Oh finished day one on six under for a share of fifth place alongside Sweden's Caroline Hedwall and Korea's Chella Choi at The Renaissance Club in Berwick, two shots behind the leading trio of Holland's Anne Van Dam, American Jane Park and Korea's Mi Hyang Lee, the 2017 champion.

In between those groups, Thailand's Moriya Jutanugarn lies a shot off the lead after her first-round 64.

Sei Young Kim, Mi Jung Hur and Hyo Joo Kim share eighth position on five-under-par.

West Australian Hannah Green is a shot further back in a pack of seven players on four under, with compatriots Katherine Kirk on three under and Minjee Lee on two under.