England's Paul Casey, who claimed his fifth European Tour win at last week's Volvo China Open, came crashing down to earth with a disappointing 74.
"It was all going against me. On the third hole I hit the flag with an approach shot and went into a bunker. Thomas [Bjorn] was laughing at me," Casey said.
Montgomerie, who recently sealed his eighth European Order of Merit title, opened with a birdie but dropped a shot on the second hole before slumping to a double-bogey on the par-five third.
The Scottish world No. 17 fought back to turn at level par but bogeyed 11 before picking up shots on 12 and 16.
Monty, who received the Order of the British Empire from Prince Charles last week, said he now needed three good rounds.
South Korea's Kang, the last Asian to win the Hong Kong Open, stormed up the back nine with five birdies from 13-17.
The 39-year-old putted his heart out, holing from 20 feet on 15 and 12 feet on 14 and 16 as he rediscovered the form that brought him seven Asian titles.
"I can't remember the last time I got five birdies in a row. My record is six," said Kang, who said he had been trekking in the 1,700m Suh-rak mountain near Seoul to get in shape.
Canada's Gibson dropped a shot on the first before setting off on a birdie streak of his own, knocking in four in a row from holes five to eight.
RSS