Juli Inkster, who finished second to Rosie Jones at this event in 1998, took third place at 4-under-par 68. Jones followed at 3-under-par 69, along with Se Ri Pak, Becky Morgan, Stephanie Louden and 17-year-old amateur Paula Creamer.
Saiki played the back side first at Locust Hill Country Club and hit a 9-iron to three feet for a birdie at the par-5 11th. She added a birdie at the 10th and hit a wedge to eight feet for another birdie at the par-5 17th.
The 38-year-old made it two in a row with a birdie at the 18th to reach 4-under around the turn.
Saiki continued her fine play on the front nine with a birdie at the par-5 fourth and knocked her tee shot to 12 feet at the par-3 ninth, her last. Saiki drained the birdie putt to complete a bogey-free round.
'It was just a very solid round for me today,' said Saiki, whose best finish at this event came in 1997 when she tied for fifth. 'I didn't hit the ball extremely well off the tee, but my misses were straight. I hit a lot of really good irons into the holes that I birdied. I've got the putter rolling well and I feel very good.'
Saiki, who has dealt with injuries throughout her career, has yet to post a top-10 finish this season with five missed cuts in 12 events.
'It's frustrating because I know that I have the ability to win,' said Saiki, who is still seeking her first win on tour. 'I can't say that I'm disappointed in the way my career has gone. I consider myself very successful to be able to survive this long and I've had a lot of good finishes.'
Kung tallied three birdies and a bogey over her first nine holes and ran home back-to-back birdies from the 11th to reach minus-four.
She stumbled to a bogey at the 14th, but countered with a birdie at the 16th. Kung then chipped her third shot to two feet for a birdie at the par-5 17th to finish one shot off the lead.
'It was a pretty consistent round,' said Kung, a three-time winner on the LPGA Tour last season. 'I was able to keep the ball in play, in the fairway and I've been pretty confident with my driver the last couple weeks.'
Inkster started on the 10th tee with three birdies and a bogey on the back side. After the turn, Inkster picked up a birdie at the first and closed with a birdie at the ninth to finish two shots back.
'The key to this golf course is get the ball in the fairway and I was able to do that quite a bit today,' said Inkster. 'So I'm ecstatic with my first round.'
Defending champion Rachel Teske carded a 2-under 70 to finish in a large group tied for ninth that features Lorena Ochoa, Betsy King and Laura Davies.
World No. 1 Annika Sorenstam, who has never won this event, collected three birdies and three bogeys for an opening round of 72.