Garcia and Campbell shot three-under 69s at Lake Karrinyup Country Club, which was whipped by dry, swirling winds later in the afternoon. Korea's Charlie Wi and Retief Goosen, last year's U.S. Open champion, were next at minus-two.
Only 14 players managed to post sub-par rounds on Thursday.
Jaidee, the reigning Order of Merit winner on the Davidoff (Asian PGA) Tour, started on the back nine and made his way out in two-under 34. He mixed three birdies with a bogey at the short par-four 14th, where he failed to get up and down out of a greenside bunker.
After adding birdies at the first, third and eighth holes, Jaidee stirred up bunker trouble again with his approach to his last hole, the ninth. This time he saved par by blasting out to 10 feet and rolling in the tricky downhill putt.
'The greens are very hard and fast,' said the 32-year-old Jaidee, 32, who served as a paratrooper in the Thai army. 'That was the only problem. I wasn't nervous -- maybe I was lucky.'
Jaidee, who turned professional just three years ago, recorded his first career victory in 2000 at the Kolon Cup Korean Open. He went on to finish sixth on the Davidoff Tour money list that year, a position he improved upon this past season with his second triumph, at the Indian Open, and 10 other top-10 showings.
He finished No. 1 on the Davidoff Tour's money list in 2001 with a record $353,060 in earnings