Smith's countryman Wade Ormsby played with eight-time WGC-Bridgestone victor Tiger Woods and both shot 73.
Woods, an eight-time victor at Firestone, took the advantage at the hard par-4 18th hole (his ninth) when he drained a 50-foot monster birdie putt to climb to three under. He started the day five off the lead and carded a three-over 73 that left him 11 adrift.
Kyle Stanley got within two shots of the lead until bogeys on the 13th and 14th holes.
At one stage, Day rocketed into a tie for second courtesy of an incredible hole-out for birdie at the par-three 15th.
Day refuses to concede the elite 71-man event to prolific victor Thomas, whose 2017 US PGA Championship title is among eight US PGA Tour victories during the past three years.
Fleetwood didn't put a foot wrong at Firestone Country Club, where he said his early tee time was a big advantage on Firestone's fast greens.
Tim Allen Calls It An 'Icy Time' For Comedians
Who makes up these rules? And as a standup comic, it's a unsafe position to be in because I like pushing buttons. It's gonna be a better show because of all you people that did this and I just hope we.
The impromptu meeting was much more than simply a pep talk, the reigning PGA Tour player of the year doesn't need that. After winning last year's Tour Championship he revealed a list that ranged from the predictable (win on Tour) to the amazingly detailed (finish the season ranked in the top 30 in scrambling).
"I was just signing my card there and realised I hadn't had a five", the 27-year-old said. "To win on a golf course like this, a championship golf course and always against a very tough field, it just felt great". When I heard everybody yell really loud I knew it was close, " Perry said. He would make just one par on the back nine to go along with three birdies, three bogeys and two double-bogeys for a four-over 40.
"I needed to go get it today and I didn't do it". The last place finisher wins $46,450, which is higher than a top 30 finish at some tournaments on the PGA Tour.
"Very similar to the first day".
"I just want to have more chances to win tournaments", he said.
Spieth was gunning for the career Grand Slam and Thomas was. well, searching for his first major championship, which came with a final-round 68, as he overtook a few of the game's other young stars in the process at Quail Hollow.
The Bridgestone Invitational field includes the top 50 players from the Official World Golf Ranking, along with members of the Presidents Cup teams and the winners of selected tournaments on the PGA Tour and other worldwide tours.