Amy Yang of South Korea fired a 67 for a one-shot advantage after the delayed halfway stage of the $A2.1 million LPGA Thailand.
Yang was one shot in front of China's Shanshan Feng and local hope Ariya Jutanugarn at the Siam Country Club Pattaya Old Course on Saturday.
Rain and unplayable course conditions saw the unfinished second round postponed to Saturday.
The 2015 champion and world No.11 Yang had six birdies and a bogey to head into the weekend rounds on 11-under 133.
"I was hitting it pretty good again. I was hitting solid, near the pin and making some putts out there," said Yang, who like Jutanugarn had to play 36 holes in the same day.
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"Tough part was staying cool on the course, especially (as) we have to play another 18."
Jutanugarn, who shared the lead with Yang in the first round, shot an unblemished round of a 68 to be tied for second on 10-under.
"I'm happy with my tee shots and approach shots," said Jutanugarn, looking for her first home win after settling for second in 2013. "Though I missed some putts, it was a good round for me."
Feng, winner of two of the last Asian Swing events, shot a 67 without a bogey.
The third round is underway.
