Smith shot scores of 71-68 in completing 36 holes on day three but at 3-under for the tournament trails Yang, who has five holes of her third round remaining, by a whopping 10 strokes.
Play was suspended Saturday due to darkness with 28 players still to complete their third rounds.
Among those is Australia’s Minjee Lee who stumbled to a 1-over 73 in the morning in her second round and is 1-over through 14 holes of her third round with four holes still to play.
Lee began round two just one shot off the lead but battled with four dropped shots over the opening nine holes and despite holing her second for eagle at the par-4 15th and making a birdie at the last she fell well off the pace.
Yang, though, stormed ahead. The 2014 winner added a second round 67 to her opening 66 and has stepped on the accelerator in round three with an eagle and four birdies in her first 13 holes.
At 17-under and showing no signs of letting up the 27-year-old is four ahead of nearest challenger, 2011 US Open winner So Yeon Ryu, and six clear of third placed Jodi Ewart Shadoff and Se Young Kim.
Ryu has completed 54 holes while Ewart Shadoff and Kim have played 17 and 13 holes of round three respectively.
Yang had little to say after her round but noted her ball striking had been key on a day when heat and humidity made it uncomfortable to be on the course.
“I was hitting it pretty good again,” she said. “I was hitting solid, near the pin, and making some putts out there.
“Tough part was stay cool on the course, especially we have to play another 18.”
Joint first round leader and local favourite Ariya Jutanugarn has been unable to keep up with playing partner Yang and has fallen seven behind with four holes to play in round three.
The World Number Two was just one off the pace after 36 holes but has been treading water in her third round with two birdies and two bogeys while Yang has stormed ahead.
She is part of a group of four players at 10-under which includes her sister, Moriya, and China’s Shanshan Feng.
World Number One Lydia Ko has again struggled to produce her best golf and after opening with 71-70 posted her first sub 70 score of 2017 with a 4-under 68.
At 10 behind her chances of winning are slim but Ko said she was pleased with an improved putting performance in round three.
“My putting was I guess a little better the third round than second and first round,” she said,
“I feel like I'm stroking it fine, but with the new putter I am trying to get a little distance control dialed in and with the new wedges trying to see how much it spins and if it doesn't.”
Of the remaining Australians Karrie Webb added a second round 71 to her opening 75 to be 2-over through 36 and remains there after 16 holes of her third round.
Young Victorian Su Oh, a contender at last week’s Women’s Australian Open, made a good start to her third round to be 3-under through her first six holes but four bogeys and one birdie since have her 3-over for the week with one hole remaining in round three.
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