As the players took a liking to a soft and exposed New Tanjong Course being used for the first time at this event, Park picked up her seventh birdie of the day on the par-four 18th to take a halfway lead at a tournament she won in 2015.
Revitalised overnight leader Michelle Wie maintained her strong showing from the opening round, the American firing a three-under 69 to join Thai world number two Ariya Jutanugarn and Korea's Hur Mi-jung in a tie for second on nine-under.
Sweet-swinging rookie sensation Park Sung-hyun is a further shot back, alongside Suzann Petterson, while defending champion Jang Ha-na and world number one Lydia Ko are also well-placed at seven-under after 36 holes.
Park endured a frustrating LPGA Tour campaign last year when she put her clubs away in May to undergo thumb surgery but returned to action with a brilliant victory at the Rio Olympics in August before opting to sit out the remainder of the season.
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Her 2015 win here was made remarkable by the fact she went bogey-free through all four rounds and after scything through 29 holes without dropping a shot this time, a repeat appeared on the cards until the setback on the par-four 12th.
"It was just really unlucky. I had a really good drive down the middle and I had mud on the ball," the 28-year-old told reporters.
"I was on the right side and I knew it was going to go left, and I aimed right but it went 30 yards left. I hit a good shot but had an unlucky bounce. Making double-bogey was a mistake."
Park, who has slipped to world number 12 as she searches for a first LPGA Tour victory since November 2015, made light of the setback and struck back with a couple of birdies coming home to cancel out her muddy misadventure.
"I was already having a really good day. I didn't want to ruin it with one bad hole and an unlucky shot. I just tried to keep the calm emotions going. There was a few birdie holes coming in, so I tried to get a couple from there," she said.
The Korean seven-times major winner added that she was just happy to be pain-free again after last year's difficult campaign and scoring well as she worked her way back into the swing of things was an added bonus.
"I had a tough time last year, so the sooner I got back, the better. Obviously, two good rounds here will definitely help with the confidence. I never took that kind of break in my whole career, so it was just something different," Park said.
(Reporting by John O'Brien; Editing by Amlan Chakraborty)
