The second ranked player in the world, Jutanugarn won the Women's British Open in her last event but withdrew from the third round at the Rio Olympics with a knee injury.
The knee didn't appear to bother her on the way to a red-hot second round.
"So I know I hurt my knee, so that's why I didn't play very good on the third round (in the Olympics)," Jutanugarn told reporters.
"And after the draw I just felt OK. I just had to rest and take care of my knee. So after that I feel like just play golf, and it didn't feel like anything changed." World number one Lydia Ko, seeking her fourth Canadian Women’s Open, is four shots behind at eight-under-par after shooting a three-under 69 in the second round.
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(This version of the story has been refiled to fixe tag in headline, no change to text)
(Writing by Jahmal Corner in Los Angeles; editing gy Amlan Chakraborty)
