UPDATE 1-Golf-"Flower power" Duangdecha blossoms in Hong Kong

* Unheralded Thai upstages quality field

* Westwood and McIlroy four shots behind

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HONG KONG, Nov 12 (Reuters) - Thailand's Udorn Duangdecha stole the thunder from a quality field to lead the Hong Kong Open with a dazzling eight-under-par first round 62 on Thursday.

Dutchman Robert-Jan Derksen was one behind while holder Lin Wen-tang of Taiwan shared third place on 64 with Frenchman Gregory Bourdy, Briton David Dixon and Thai Thongchai Jaidee at the $2.5 million event co-sanctioned by the European and Asian tours.

Race to Dubai leader Lee Westwood carded a 66, a score matched by fellow Briton Rory McIlroy who is second on Europe's money list.

Asia's first major winner Yang Yong-eun of South Korea and former British Open champion Mark O'Meara also fired four-under-par 66s.

Derksen won a gold bar for a hole-in-one in Hong Kong two years ago and he set the early pace after birdying five of the last six holes, his only blemish a three-putt at the 16th.