TOKYO, Sept 21, 2008 (AFP) - Indonesian ace Sony Dwi Kuncoro upset world number-one and defending champion Lee Chong Wei 21-17, 21-11 to win the Japan Open here Sunday, avenging his quarter-final defeat to the Malaysian at the Beijing Olympics.

Top-seeded Lee, struggling for form following his Beijing final defeat to China's Lin Dan, jumped to a 16-12 lead after 10-all in the first game.

But Dwi Kuncoro, seeded second here and ranked sixth in the world, caught Lee at the 17th point and went on to win the set as the Malaysian slumped with a number of unforced errors.

The 24-year-old Indonesian led the second game all the way from an opening 5-0 gap, outpacing Lee with a variety of shots including three solid jumping smashes.

Dwi Kuncoro, who won the Indonesia Open in June, sealed his second Super Series title of the year when Lee's backhand shot at 20-11 landed outside the baseline.

The Indonesian, who bowed to Lee 21-9, 21-11 in Beijing, was scheduled to compete next week at the eighth Super Series event, the China Masters in Changzhou. But Lee has pulled out of the event to rest.