Thomson won the the Glenfarclas Open in Renfrewshire within a month of joining the paid ranks.
After rounds of 68 69 at Moor Allerton he is within striking distance of Clandeboye’s Jonathan Caldwell, who leaped to the top of the leaderboard by adding a seven-under-par 64 to his opening 70.
Malton & Norton’s Chris Halley, still seeking his first victory on the tour, is one adrift of Thomson with scores of 68 70.
Former Yorkshire county player Thomson made it to the turn level with the card, but with only four pars.
He followed a bogey at three with an eagle at five, a birdie at six and further bogeys at seven and nine.
Coming home, he sandwiched a bogey at 13 with birdies at 12 and 14, and another birdie at 16 got him to five under for the event.
Halley started his round at the 10th and opened with a birdie, but a dropped shot at 17 had him ‘out’ in level par.
Further shots were surrendered at the first and fourth before he, like Thomson, eagled the fifth before birdieing the ninth.
Cookridge Hall’s Tom Broxup, one of two amateurs in the field, missed the cut on 147 (71 76).