Tseng unearthed six birdies and made only one bogey in a five-under par round as she defends the tournament she won last year.
World number five Park produced a bogey-free round of 65, making four birdies on the first nine to catapult herself to the top of the 78-strong field in Taoyuan County in Northern Taiwan.
“Obviously with that number, everything went really well today,” Park, who earlier this month captured her second victory of the 2012 season at the Sime Darby LPGA Malaysia, said.
“I hit the ball great. I mean I hit a lot of short irons in, so I hit a lot of shots close and I was able to make a lot of birdies.”
A group of four players are tied for third on 68 and they include Nicole Castrale and Danielle Kang of the United States, Hee Young Park of Korea and Pornanong Phatlum of Thailand.
Scotland's Catriona Matthew, who lost a play-off at the Hana Bank Championship in Korea on Sunday, is in contention after a 70,
First round leaders
Inbee Park (South Korea) -7
Yani Tseng (Taiwan) -5
Nicole Castrale (US)-4
Danielle Kang (US) -4
Hee Young Park (South Korea) -4
Pornanong Phatlum (Thailand) -4
Paula Creamer (US)
Suzann Pettersen (Norway)
Lizette Sala (US) -3
Chella Choi (South Korea) -3