At four-under 140 aggregate, the Thai girl is one stroke clear of the other overnight joint leader Valentine Derrey of France, who managed a three-over 75, and Ladies European Tour (LET) sensation Charley Hull of England, who rose from fourth to tied second position after posting an even-par 72.
The 20-year-old Indian amateur, Gauri Monga, underlined her class as she carded a two-under 70 in the second round to jump from overnight 13th to fourth position, three strokes behind the leader, in company of Thailand's Saraporn Chamchoi.
Thidapa had an unfortunate start today as she dropped three strokes on the front nine. She gathered momentum on the back nine and two birdies (10th and 18th) and a bogey on 13th helped her stay in lead.
Thidapa, who started her round in the foggy morning, said she found herself struggling in the tricky greens and tough pin positions. "My putts for birdie were all short on the back nine. The greens were trickier and the pin positions were harder. I think it's harder playing in the morning than in the afternoon," she said after her round today.
Valentine rued her putting and is keen to make amends on the final day.
"I'm going to practice my putting and we'll see what happens tomorrow. I didn't play bad; I just had two bad holes. My putts weren't bad but were hitting the edge all the time so if they drop it could be a different story."
Hull, who has four runners-up finishes this year, jumped to the sole lead after firing birdies on 11th and second holes. A 10th tee starter, Hull had to be content with her second position after dropping bogeys in succession on third and fourth.