But he saved his best for the final four holes.
At one time seven players were tied for the lead at seven-under and then again at eight-under with nobody able to gain separation until Thomas ripped a mighty three-wood second shot and then drained his eight-foot eagle putt at 18 sparking thundering roars from the massive gallery.
Justin Thomas demonstrated impressive ingenuity to hole an incredible putt for birdie which ignited his charge up the leaderboard at the US Open.
When he eagled the par-5 18th, he became just the fifth player ever to finish with a score of 63 in U.S. Open history, making him the first player since Vijay Singh accomplished the feat at Olympia Fields in 2003.
Johnny Miller owned the previous best round of eight-under 63 set at the 1973 U.S. Open at Oakmont.
Thomas birdied No. 17 to reach 63 and take the outright lead.
Escaped Georgia inmates captured in Tennessee, officials say
Sills said investigators now have nighttime surveillance video that apparently shows the two men between Madison and the quarry. Authorities warned that the men, who had escaped with the guards' 9 mm pistols, were considered very risky .
Thomas, decked out in fluorescent pink trousers, was on the move quickly with a birdie-birdie start and had an even hotter finish to his front nine, carding birdies on four-of-five closing holes, including the last three to move to seven-under.
His run continued just two holes later, where Thomas drained a 26-foot birdie putt to move himself in to the lead (although he was quickly joined by Tommy Fleetwood) at nine-under-par.
Thomas is sponsored by Polo Golf, so you know where to look for those pink trousers.
Justin Thomas had himself a day. "I had no idea about the relation to par, so that was definitely a big bonus".
It may have been just Saturday at the US Open, but Thomas will more than likely be up there in one of, if not the final group tomorrow.
"Regardless, I'm going to have to play a good round tomorrow", Thomas said.