Tseng, who won the Founders Cup in Phoenix last weekend, shared the lead after the first round before striking out on her own for a two-shot lead after the second.
And a round of 69 on the third day in Carlsbad, California, featuring three birdies saw the Taiwanese 23-year-old add another shot to her lead with only South Korea’s Jiyai Shin looking likely to challenge.
"I guess I got some good breaks and I got some bad breaks," said Tseng, who is 12-under for the tournament. "This is golf. Some things are going to happen.
"The green are pretty bumpy," Tseng said. "So when I hit it just straight, it bumped to the right or to the left. I just tried my best, but I was just thinking it was unlucky.
"I kind of feel pretty relaxed," Tseng said. "I was pretty happy. I'm going to go putt a little bit and practice a little bit. I'm really looking forward to tomorrow."
Shin enjoyed a mixed round, her seven birdies tempered by three bogeys around the turn as she carded a round of 68 to sit second.
“In California, here they have a lot of Korean people, so they're watching and cheering for me, so it feels like I'm really ready to go when I play,” Shin said. “The last couple years, I played good in this tournament, so I only have good memories."
The best round of the day came from Shin’s compatriot Sun Young Yoo, who recorded five birdies on her way to a 67 that saw her move into a share of third place alongside Caroline Hedwall.
Si Re Pak, who shared the lead with Tseng after the first round, is a further shot back in fourth while Inbee Park, Chella Choi, Jodi Ewart and Alison Walshe share sixth place on four-under par 212.