World No. 1 Annika Sorenstam fired a 6-under 66 to jump into third place at 6-under-par 138.
Marisa Baena, who shared the lead after round one with Koch and Lynnette Brooky, stumbled to a 3-over 75. She dropped into a tie for eighth at 3-under-par 141.
Sorenstam opened with a birdie on the first for the second straight round. She parred her next five holes, then made her run. The Swede dropped in a birdie at the seventh from 5 feet out.
The 34-year-old came right back with a 6-foot birdie putt on the eighth and made it three in a row with a two-putt birdie on the ninth. Sorenstam tripped to a bogey on the 10th, but got that stroke back with a birdie on the 14th.
Sorenstam moved to minus-5 with a birdie on the par-4 16th. She closed with a two-putt birdie at the last to get within two of the leaders.
'Obviously I am very happy about my round today,' said Sorenstam, who won here in 2000. 'Yesterday I was a little frustrated. I thought I hit the ball really well and I had a lot of opportunities. Today I do not feel like I left that many out there. I feel good about how I put my score together. I feel I hit the ball well and had a lot of opportunities and converted most of them.'
Creamer, who won the Sybase Classic earlier this year, got off to a fast start with birdies on one and two. She faltered to a three-putt bogey on the par-4 fifth.
The 18-year-old then flew up the leaderboard. She birdied the par-5 seventh from 10 feet out and then birdied the eight and ninth to make the turn at minus-8.
Creamer capped a run of four straight birdies as her 5-foot birdie putt at the 10th dropped into the cup. However, she stumbled to back-to-back bogeys from the 12th to drop back to 7 under. Creamer closed with a 9-foot birdie putt at the last to join Kim in the lead.
'I have been very consistent,' Creamer said. 'I have given myself a lot of chances out there. I missed a lot, but I made some saves as well. I am pretty content. I played well today.'
Kim birdied the second to get to minus-5 overall. After four straight pars, the 21-year-old three-putted bogey at the seventh before bouncing back with consecutive birdies from the eighth.
Around the turn, she climbed to 7 under with a 4-foot birdie putt on the par-4 13th. Kim, who won the 2004 Longs Drugs Challenge, made it two in a row as she kicked in a 2-foot birdie putt at the 14th.
'I hit a lot of iron shots coming into the green and I missed quite a few putts inside 10 and 15 feet that could have gone in, but all in all it was a very, very satisfying day,' said Kim. 'The way I see it is that if I did not miss those, then I would not have made the ones I did.'
Baena was joined in a tie for eighth at 3-under-par 141 by Maria Hjorth (72), Karine Icher (70) and Sophie Sandolo (71).
Michelle Wie managed a 2-under 70 and is tied for 23rd at 1-over-par 145. The 15-year-old birdied two holes on the front nine, while she also bogeyed the eighth. Around the turn, Wie birdied the 10th and the closed with eight straight pars.
Brooky faltered badly in the second round. She sputtered to an 8-over 80 and tumbled into a tie for 33rd at 2-over-par 146.