The defending champion from Korea has carded back-to-back 69s to stand at eight-under-par after 36 holes.
Her nearest challenger is England???s Holly Clyburn whose second day 65 is the lowest score of the week so far by three shots.
The 24-year-old from Cleethorpes is tied with China???s Xiyu Lin but there is then a four stroke gap to three players who are tied-for-fourth.
These include Becky Morgan of Wales who had shared the 18-hole lead with Park on Thursday.
The 40-year-old could only shoot a second round 74 and is five adrift at the halfway stage.