The 19-year-old Lindrick member is tied second on 212, just one back of the 54-hole leader, Ireland’s Cormac Sharvin who carded 67 at Notts (Hollinwell).
Bedale’s Daniel Brown is tied 32nd on 219 after three consecutive rounds of 73 and Huddersfield’s Nick Marsh is tied 50th (75 69 78).
Thomson is finally returning to full health after some medical issues earlier in the season and his improving fitness is being complemented by an improving golf game.
“I did play some real golf out there,” he said. “I knew my game wasn’t far off, it was a case of piecing it all together.
“In the second round (a 76 after an opening 70) I had some real bad luck on the course and it was a really frustrating day.
“(In the third round) I parred the first then double bogeyed the second and thought it was going to be another seriously long day.
“Then on the third hole my second was slightly long onto a road leading to the car park and it’s an integral part of the course so I didn’t get relief.
“I ended up chipping off the road to about 6ft and holed it – and then had five birdies in a row.”
That five-hole five-under sequence sparked by an excellent up and down saw him driving straight and far and putting his approach shots close.
“When I had the five birdies on a spin I don’t think any of the putts was outside 10ft,” he said.
“The whole momentum of my game swung with getting up and down off the road and I got on a roll.
“I started hitting it really well off the tee and that is quite key around this course.
“Although the rough isn’t particularly high it is quite long and wispy. You can’t attack the flag from out of the rough, but from the fairways you can and I started hitting it quite close.”
A birdie at 17 put him seven under for the round, but the wind dragged his final tee shot into thick rough.
“It sniped the head of my 9-iron and the shot came up 50 yards short of green in real thick stuff, and in a hole where someone else had played from. I hacked it out, duffed my chip to about 25ft – and holed it for a bogey. Even though it was a dropped shot it felt like a par.”
Feeling better physically has helped Thomson’s thought processes out on the course.
“My thinking out there is a lot clearer now and my head’s a lot clearer whereas before when I was feeling rough everything became a chore. I feel like I’m back on the right road.”
Brown birdied one and five but bogeyed nine to be out in one-under 35 before coming home in 38 with a birdie negated by an earlier bogey at 12 and double bogey at 13.
Marsh, who had shot 69 the day before, could only squeeze one birdie from the course in round three while suffering three bogeys and two double bogeys.