With a sixth PGA Tour win since January last year, he's not far off top spot.

Closing the event at Florida's PGA National with a two-under 68, Thomas booked a sudden-death playoff against Luke List (69) when the pair finished regulation play at eight under.

On the first extra hole, Thomas demonstrated his go-for-broke mentality when he went for the par-5 18th on his second shot and finished off fellow American List with a two-putt birdie.

The 24-year-old joins Spieth and Tiger Woods as only players in the past 30 years to have eight or more US Tour wins before the age of 25.

Thomas has faced comparisons to three-time major winner Spieth throughout his short but brilliant career.

But he said rising to World No.3 and overtaking Spieth for the first time meant nothing.

"Not really, because there are still two more spots that I want to climb," Thomas said.


Thomas reacts after making the winning putt on the 18th green during a playoff in the final round of the Honda Classic at PGA National Resort and Spa. PHOTO: Sam Greenwood/Getty Images.

He is now within striking distance of reeling in World No.1 Dustin Johnson.

"I think it would be ludicrous to not be (my) goal," Thomas said.

"I think it's pretty well known that any golfer wants to be No.1."

The Kentucky native enjoyed a breakout 2017, with five wins including a maiden major at the USPGA Championship, along with the $US10 million FedEx Cup title.

Thomas felt his second win of the 2018 season could open the floodgates for another big year.

"This definitely takes the pressure off me; I was starting to feel a little bit," Thomas said, having defeated Marc Leishman in a playoff at the US Tour event in Korea in October.

"Obviously, I would love to win five times every season but when I give myself a chance to win, I feel comfortable I can get it done."

Sweden's Alex Noren finished solo third at seven under, while 14-time major winner Woods signed off on the third event of his injury comeback with a 70 to finish outright 12th at even par.

Meanwhile, Adam Scott and Greg Chalmers earned their best finishes for the 2018 US season.

Scott shot 69 to finish at one over and tied for 13th, while left-hander Chalmers signed off with a 67 to share 17th at two over.

- Evin Priest, Australian Associated Press