The 29-year-old smashed the course record for the tough Black Knight Course at DLG Golf and Country Club in Gurgaon with an eight-under-par 64 in the second round.
The stunning effort swept Thomson clear of the field on 10-under-par as she seeks her breakthrough victory on the Ladies European Tour.
“My performance overall was really good,” said the Scot after signing for eight birdies in matching halves of 32.
“My irons were solid today, so that was the main reason for scoring low, and then I had 26 putts, which helped.”
The Aberdonian, who missed the cut in her previous three events on the circuit, added: “I stuck to my strategy and went through my routine.
“I played solid yesterday but just didn’t hole as many putts. My round was as good today, I just holed more putts.”
It was Thomson’s lowest score on the LET, where she first played in 2009 after turning pro before taking a break from the game and becoming a policewoman.
“Once I’d had my break, I saw all the girls that I’d played amateur golf with doing really well,” recalled the Meldrum House-attached player.
“I had done my stint with the police - I was in the force for two years - and I wanted to come back. I knew I had something more to give and I didn’t give it my best when I first turned professional, so I decided to give it another go.”
Thomson used the LET’s development circuit, the Access Series, as a “stepping stone” to get back on the main Tour this season.
“I was much more mature and realised how lucky I was to be playing golf and doing this as a career,” she added.
“I spent about three years on the Access Series trying to get my card for the LET and managed to do it last year.”
Now Thomson has set up a golden opportunity to land Scotland’s first title triumph on the circuit since Kylie Henry chalked up the second of her two victories in 2014.
All sitting on seven-under, her closest challengers are French duo Camille Chevalier and Celine Boutier, Australian Sarah Kemp and Indian Vani Kapoor.
Henry was the only other Scot to make the cut, carding a 70 to sit joint-26th on one-under-par.