Tseng has won three of the first seven tournaments this year.
Hjorth returns to the site of her fifth LPGA victory after what turned into a fun family trip last year. Husband Shaun McBride carried her bag and then-2-year-old daughter Emily was on hand.
"It's always great to be back at a place where you've won obviously, and defending is always special," Hjorth said. "There's obviously a lot of memories that come back. You go out there and play and you see a lot of shots that you hit last year and you still see a lot of putts that you made from the tournament.
"And obviously a lot of great memories with my husband on the bag and my daughter ...so it was a nice family get together for the week. Having a win as well was even more amazing."
She's had a slow start in 2012, missing the cut in two of her six events. Her best finish so far is a 25th-place tie at the HSBC Women's Champions in Singapore.
"I feel pretty good about my game and I've worked hard on it, especially my putting," Hjorth said. "Hopefully it will come together. I feel it's very close, and coming out here and having good memories, hopefully that will bring my game up a little bit and have a good finish."