Lee, who was aiming to capture his second career win on the PGA Tour, revealed after his third round yesterday that his second child was born two months prematurely overnight.
Lee's wife was scheduled to deliver their child around Christmas.
Thomas and Lee made it mostly a two-man show Sunday.
They entered the final round tied and stayed that way through the front nine.
Thomas birdied 14th to take one-stroke lead, then went up by two when Lee bogeyed the 15th after missing a 10-foot par putt and Thomas made a two-footer for par.
After going from greenside bunker to bunker on the 16th, Green bogeyed again and fell three behind.
But Thomas bogeyed the 17th after his 12-footer for par lipped out, reducing the deficit to two strokes.
On Saturday, Thomas had a three-stroke lead heading into the 18th ahead of a three-shot swing when Thomas bogeyed and Lee made a long eagle putt.
On Sunday, there were no such late miracles for Lee: Thomas and Lee both birdied the 18th, with Lee lipping out on his eagle putt to finish with a 69.
Hideki Matsuyama (65), last year's runner-up Gary Woodland (66) and Australian Cameron Smith (69) finished tied for third, five behind Thomas.
Jordan Spieth closed with a 71 and was tied with four others at 12-under.
Phil Mickelson finished with a 68 and Jason Day with a 71, both at 7-under.
The PGA Tour's second of three weeks in Asia continues next week at the Zozo Championship in Japan — which will feature Tiger Woods — and ending with the World Golf Championship event in Shanghai.
- With AP
