Kiradech Aphibarnrat turned in 31 at the Old Course to open up a one-shot lead early on day two of the Alfred Dunhill Links Championship.
After tackling Kingsbarns in 70 on Thursday to sit three off the lead, he picked up five birdies at St Andrews to get to seven under and lead by one ahead of Frenchman Romain Wattel and overnight co-leader Nicolas Colsaerts.
Welshman Bradley Dredge, Scot David Drysdale, Ireland's Paul Dunne and England's Oliver Fisher were then at five under.
Thai Aphibarnrat is a three-time European Tour winner but has just three top tens this season, although he found his form in some fashion at the home of golf, birdieing the first, fifth, sixth, eighth and ninth.
Big-hitting Belgian Colsaerts was also playing the Old Course and he birdied the first after finishing with two gains at Kingsbarns on Thursday.
KLM Open champion Wattel was playing Kingsbarns after carding a very respectable 70 at Carnoustie on day one and he was four under after a roller coaster first seven holes containing five birdies and a bogey.
Drysdale and Dredge were also playing Kingsbarns and they were two and three under for the day after seven and three holes respectively.
Fisher was one under for the day after one hole with a birdie on the tenth at Carnoustie, while Dunne had a par on the first at the same layout.
French duo Romain Langasque and Joël Stalter, defending champion Tyrrell Hatton, Swede Joakim Lagergren, Dutchman Joost Luiten, Australian Aron Price and German Marcel Siem were then four under.