The pair finished with a one shot advantage over American Brittany Altomare while a group of 11 players were within five shots of the lead after the second round at the Miramar Golf Country Club in New Taipei city.
The current world number one Ryu So-Yeon, also of South Korea, climbed to seventh place with a 4-under 68, rising from 23rd place after hitting a disappointing 1-over 73 in the opening round.
Shin said she felt "really good" after finishing the day with seven birdies against two bogeys.
"I've had some really good putts today, really good shots. I had a really good break back there on the 18th hole," she said.
Overnight leader Ji carded a 1-under 71 with two bogeys and two birdies to remain atop the leaderboard.
"Not as great as yesterday but I don't feel really bad," said Ji, who added that she felt she had improved on the last nine holes after struggling in the first half.
Altomare scored five birdies and a bogey on both the front and back nine to finish at 6-under 66.