Smith spent much of Sunday's final round sliding down the leaderboard as others charged but finished birdie, birdie, eagle in his last three holes to recoup the damage and post a closing three-under 69.

Inaugural champion Thomas staved off a challenge by Korean-born New Zealander Danny Lee to claim his second CJ Cup title in three years with a two-shot victory at Nine Bridges.

The overnight leaders were level for the first 13 holes before Thomas surged ahead with a birdie on the 14th, while Lee bogeyed the 15th and 16th to effectively drop out of contention.

Thomas eventually signed off with a five-under 67 for a winning total of 20-under 268, while Lee carded 69 to finish in second place.

"It was a very, very tough day," Thomas said.

"Danny made it extremely difficult. He really made a lot of putts, a lot of unbelievable up and downs to kind of keep me from getting all the momentum. I really, really played solidly today."

"My dad turned 60 last week, so maybe it's a little 60th birthday gift to him."

Smith shared third place with Hideki Matsuyama and Gary Woodland. PHOTO: Jung Yeon-je/AFP/Getty Images.

It has been a difficult week for Lee whose second child, originally due closer to Christmas, was born prematurely last Sunday and is in an incubator.

"Before I tee off my very first tee shot on Thursday, if someone's going to give me solo second, I would take it in a heartbeat. It is a good week but also very disappointing," he said.

"I really wanted to win the CJ Cup. It means a lot to me to win it in front of the Korean fans and all my Korean family but it is what it is. I gave my best out there today and solo second was the best I could do."

Hideki Matsuyama (65), Gary Woodland (66) and Smith (69) shared third place at 15-under.

A further three shots behind was Jordan Spieth, who returned 71. Next-best Australian Matt Jones tied for 20th after a 65, while Phil Mickelson finished with 68 to be joined by Jason Day (71) at seven-under.

The PGA Tour's three-event Asian swing now moves to Japan where Tiger Woods will compete in the Zozo Championship before Shanghai hosts the World Golf Championships from October 31.