Annika Sorenstam, a two-time winner of this event, fired a 5-under 67 and is tied for third place. Defending champion Se Ri Pak (68), Lorena Ochoa (68), Becky Morgan (68), Rachel Teske (68) and Nabisco Championship winner Grace Park (71) joined Sorenstam in third place at 9-under-par 207.
Song, who shared the overnight lead with Lorie Kane, played smart, solid golf on Saturday. She parred her first four holes, then knocked a 7-iron to 8 feet to set up birdie at the par-4 fifth.
Song parred her next eight holes before reaching the par-4 14th. She hit a sand-wedge to 20 feet and drained the birdie putt to go past Kim into first place.
Those two birdies were all Song needed to take the lead with one round to play.
Song, a tour rookie, will be in search of her first victory on the LPGA Tour. She came close at the end of March at the Nabisco Championship when she ran home a 30-foot eagle putt at the 72nd hole. Park sank a 6-footer for birdie to take the title, but Song might now be ready to visit the winner's circle Sunday afternoon.
'I played in so many events, I'm getting more comfortable out here,' said Song. 'I've been around the lead quite a few times, not only in LPGA tournaments, but even in amateur golf. I can certainly fall back on those experiences.'
And what better birthday present than win No. 1?
'That would be nice,' she said. 'I wouldn't mind that.'
Kim, who has not won on tour since the middle of the 2002 campaign, also collected her first birdie at the fifth but unlike Song, Kim's birdie putt was from 50 feet. Kim holed a 15-footer for birdie at the eighth and sank a 6-foot birdie at the 12th.
That was the last birdie for Kim but now she is within striking distance.
'I missed a couple of birdie chances,' said Kim. 'I like my shot. My putting is very good and I feel more confident. I am looking for the win.'
Park was tied with Kim at 10 under par heading into the par-5 closing hole but drove her tee ball into water on the left side. She missed a 5-footer for par to fall into the logjam in third, with formidable competition like Sorenstam and Pak.
'To be honest, I don't care who's up there,' said Park, who won her first major title at the Nabisco Championship. 'I look at the leaderboard and I see the names, but I don't care whether it's Joe Schmoe or Annika Sorenstam.'
Sorenstam mixed six birdies and one bogey on her round while Pak tallied six birdies and two bogeys.
Kane struggled to a 1-over 73 and is tied for ninth with Janice Moodie (68), Michele Redman (70), Rosie Jones (70) and Natalie Gulbis (72). The group is knotted at 8-under-par 208.