Beginning the day joint-overnight leader alongside??Brittany Lang and Tseng Yani, Lewis struck four successive birdies from the fourth to reach the turn in 32, before making four further gains in a flawless round.
The 30-year-old heads in to the weekend on course for her fourth top five finish at the Siam Country Club??in a row and with a 12th career title a real possibility.
“It really was a pretty easy day,” Lewis said. “I didn’t cause myself too much stress. Hit a ton of greens, which is what you have to do on this golf course.
“It got off to a bit of a slow start, but about midway through the front nine it kind of caught fire with the putter and I started hitting some shots close.”
Korea’s Amy Yang kept in contention with a second round 66 to move 11-under, with home favourite Ariya Jutanugarn in the group a further three strokes adrift. Jutanugarn, who finished runner-up two years ago after losing her nerve on the final hole, carded a three-under 69 that included six birdies.
Overnight joint-leader Yani posted an eagle on the par-five seventh but ended her inconsistent round level par, with fellow early pacesetter Lang a further shot back on five-under four the tournament following an error-strewn second day.??
Defending champion Anna Nordqvist was five-under after ten holes but dropped three shots on her back nine, while world No 2 Inbee Park posted another disappointing round with four bogeys in her two-over 74.??