Tseng, tied for the first-round lead after 67, had a 9-under 135 total on La Costa’s Legends Course.
The 23-year-old Taiwanese star won the LPGA Founders Cup on Sunday in Phoenix for her 14th LPGA Tour title and second in four events this year. She led the tour last season with seven victories – including major victories in the LPGA Championship and Women’s British Open – and finished the year with 12 worldwide titles.
Pak had 66. Jiyai Shin, Alison Walshe, Jodi Ewart and Caroline Hedwall were 5- under. Walshe shot 66, Ewart 69, Shin 71, and Hedwall 72.
Michelle Wie missed the cut with rounds of 77 and 79.
EUROPEAN TOUR: In Agadir, Morocco, Phillip Price shot 6-under-par 66 to lead the Hassan II Trophy by a stroke after strong wind and thunder delayed the start of the second round by 5½ hours.
Price’s last victory came at the 2003 European Open in Ireland.
He had six birdies for the day, making three in a row starting with his sixth hole, and was at 10-under 134. Jose Manuel Lara was at 9-under after 65. Joakim Sjolholm had 66, leaving him at 8-under.
Matteo Manassero kept alive his hopes of qualifying for the Masters Tournament after 70 put him at 5-under.
The 18-year-old Italian must win this European Tour event to have any chance of getting back to Augusta National. He was low amateur in 2010.
CHAMPIONS TOUR: In Saucier, Miss., Tom Pernice Jr. took full advantage of soggy conditions in the Mississippi Gulf Resort Classic.
In his first Champions Tour event this year, Pernice was 7-under through 12 holes before play was suspended because of darkness. The 52-year-old Pernice has played eight PGA Tour events this season.
Chien Soon Lu and David Eger – who won the inaugural tournament in 2010 – were a stroke back. Lu played 16 holes, and Eger completed 15.
Only a handful of players completed their rounds because the start was delayed more than four hours after more than 9 inches of rain fell on Fallen Oak in 36 hours.
Fred Couples was 3-under through 12 holes.
NATIONWIDE TOUR: In Broussard, La., Camilo Benedetti shot 8-under-par 63 to take a one-shot lead over Brendan Pappas (67) at the Louisiana Open.
Benedetti is at 13-under 129 at Le Triomphe Country Club.
Augusta native Scott Parel shot 70 and is tied for 27th at 136.
Aiken’s Matt Hendrix shot 69 and missed the cut, finishing at 139.