The 28-year-old from Shellharbour, whose highlight of the year was becoming the first man to fire a hole-in-one on the new 17th hole at Royal Liverpool in The Open, had to give best to remarkable Thai teenager Denwit Boriboonsub in the $US 1 million ($A1.5 million) event in Riyadh on Sunday.

Boriboonsub, just 19, won his third event in successive weeks to claim the $US180,000 ($A270,000) first prize, ousting veteran former Open Champion Henrik Stenson by three shots with Smyth a further shot back.

The Australian, who banked $A1.1 million in a single week last year during the infancy of the LIV Golf project, shot a final-round, four-under-par 67 at Riyadh Golf Club to try to pressurise the teenager.

But he had to settle for a substantial third-place prize pot of $US63,000 ($A94,000) to finish what's been a fine year, as he leapt three places to fourth in the final Order of Merit standings which were headed by American Andy Ogletree.

The Thai teenager won for the third time in as many weeks. PHOTO: Phil Lakatos/Asian Tour.

None of the opposition could cope with the continuing, seemingly nerveless excellence of Boriboonsub, who had won the Aramco Invitational two weeks ago on the Asian Development Tour and followed up with victory at the Thailand Open last week.

The youngster trailed compatriot Phachara Khongwatmai by one going into the final round, but his brilliant 64 on the final day was the joint-lowest round and enabled him to finish on 18-under after he had recorded eight final-afternoon birdies.

Armed with water bottles, his fellow competitors ran on to the green and drenched the teenager, who was left muttering incredulously afterwards: "It is an unbelievable feeling because it is incredible winning three weeks in a row. It is like magic."

Smyth's fellow Australian Todd Sinnott, who had been the co-leader at halfway and was only two shots behind going into the final round, slipped down the field with a 70 which left him in joint-10th place on 11-under.

As well as picking up a $US20,000 ($A30,000) cheque, the performance, just as importantly, ensured that Melbourne's Sinnott would keep his Asian Tour card for 2024 on the $US35 million ($A52 million) circuit.