San Francisco Frontiers - World number one Ko, Yang share lead in Singapore

Ko was two shots off the pace at the beginning of the day but got off to a good start with an opening birdie, before sinking another pair of birdies on holes seven and eight.

She reeled in another two birdies on her closing three holes at the Sentosa Golf Club in Singapore.

Yang also carded 67, firing seven birdies and two bogeys, keeping her on course for her fifth LPGA victory.

The leaders hold a one-shot advantage over Canada's Brooke Henderson, American Megan Khang and Atthaya Thitikul of Thailand after the trio returned with 68s to share third place.

Despite taking the lead, Ko -- who won five times on the LPGA Tour last year -- said she was "not really satisfied".

"My swing felt very different on the front nine, and I thought I played better on the back nine," she said.

"I'm not sure if that was a mental thing or I needed to warm up more before the start of the round."

"I just wanted to make more birdies than yesterday," said the South Korean, who had marked her opening round with six birdies, a double-bogey and bogey.

Yang, who finished tied 12th at the tournament last year, is focused on trying to stay relaxed for the rest of the tournament.

"I want to keep it simple and not overthink too much," she said.

"There are things which you cannot control on the golf course, and what I can only do is really to prepare well for each shot."

Overnight leader Patty Tavatanakit of Thailand struggled to a 74, slipping to a share of 21st place, five shots behind the leaders at the $1.7 million tournament.

X.Roberts--SFF