HONOLULU — Inside the golf shop at Harmony Landing Country Club in Goshen, Ky., there are 129 golf balls on a rack. Each ball represents one of Justin Thomas’s wins, starting in elementary school. In a nearby box, there are balls from his holes-in-one.

Thomas’s father, Mike, the club’s head professional since 1990, will soon add two more balls to the collection, because his son won the Sony Open at Waialae Country Club in Honolulu on Sunday, his second victory in two weeks. In the opening round, Thomas became the seventh player in PGA Tour history — and, at 23, the youngest — to shoot a 59.

“We’ll get a separate glass case for that one,” Mike Thomas said of the 59 ball, joking about what it might fetch on eBay. “I can’t have that one just sitting out in the shop.”

The ball might be worth even more a few years from now.

No one is playing better than Thomas at the moment. In his Sony Open victory, Thomas closed with a final-round 65 that included a birdie on the final hole and finished at 253 for the week, breaking the Tour’s 72-hole scoring mark by a stroke. During the week, he also matched the Tour’s lowest opening 18-hole score, broke the 36-hole mark and tied for the lowest 54-hole total.