Cameron Smith has fallen ruefully short of his third win of the year in one of the most extraordinary tournament finishes that golf aficionados could remember.

Smith looked unusually content to settle for second to New Zealander Ben Campbell at the Hong Kong Open after Thai Phachara Khongwatmai's brazen conduct late in the final round.

Holding a one-shot lead over Smith with three holes to play, Khongwatmai cut his drive on the par-4 16th into the local flora at Asian Tour's Hong Kong Golf Club.

After failing to hack his second shot out of the bushes, Khongwatmai virtually held the tournament to ransom as he agonised and antagonised over his next move.

He pushed the rules to the boundary in seeking an unplayable lie, and left the mild-mannered Smith and especially Campbell exasperated with his attempts to gain an advantage from his own poor play.

While Khongwatmai selfishly sought relief from his lie in the bushes as his playing partners had to wait, Smith and Campbell protested.

"He's broken these branches here," Campbell told officials, to no avail, while pointing to the vegetation in question. "Look at that, these just got broken ... Wow."

As Smith walked away, seemingly in dismay and disgust while possibly also trying to retain focus, international TV commentators couldn''t believe what they were witnessing.

"I've never seen this before," one said.

"You get the impression his playing partners are not happy."

Eventually, after some 20 minutes of delay, Khongwatmai - down on his knees with no sight of the ball after changing clubs twice - attempted his shot.

"He's not thinking clearly," a commentator said. "I really don't think he is. This could go horribly wrong. His head must be in a mincer at the moment."

Miraculously, Khongwatmai chopped the ball out of the bushes and next to the fairway. He eventually carded a double-bogey six as Smith made par for a two-shot swing.

From one behind, Smith was one up heading to the penultimate hole.

Almost inevitably, though, there was another twist. Campbell and Khongwatmai birdied the 17th to join Smith in the lead walking to the last, the toughest hole on the course.

It was advantage Campbell when the Kiwi stuck his approach to within 15 foot as Smith was forced to lay up after spraying his tee shot right and under the trees.

Despite Smith almost holing his third shot and saving par, Campbell stole the trophy with a brilliant birdie at 18 to hit the lead for the first time in a tension-filled final round.

Campbell closed with a four-under 66 to finish at 19 under for the championship, one better than third-round leader Smith (68).

Antipodean fans could probably see the wry smile on Smith's face when Khongwatmai badly pulled his short par putt on 18 to fall into a tie for third at 17 under, with a Sunday 69, with fast-finishing Canadian Richard Lee (64).

Despite the near miss, Smith's runner-up showing - after two wins on the LIV Golf tour in 2023 - is the near-perfect preparation for the defence of his Australian PGA Championship title in Brisbane next week.