Ko is nine-under and has a share of second with American Gerina Piller, two shots back from leader Inbee Park, from South Korea.
Our fast-starting women's kayaking four are another strong medal chance.
Jaimee Lovett, Kayla Imrie, Aimee Fisher and Caitlin Ryan powered into tonight's 500-metre final in resounding style, dominating their semifinal at Rodrigo de Freitas lagoon.
"We've got the potential, we've done the training and now it's becoming more real as time goes by," said Ryan. "This year we've set ourselves in medal contention."
Tonight is also the women's triathlon, with Andrea Hewitt and Nicky Samuels in action for New Zealand.
And, tomorrow afternoon, veteran Nick Willis will be bidding to add to the silver he won at the 2008 Beijing Games in the 1500m final.
KIWIS IN ACTION TONIGHT
Golf: Women's individual strokeplay, final round - 11.44pm
Kayaking: Women's K4 500m final - 12.32am
Triathlon: Women's race - Andrea Hewitt, Nicky Samuels - 2am
Athletics: Men's 1500m final - 12pm