KUALA LUMPUR (AFP) - Three-time champions South Korea reached their seventh Sudirman Cup final when they defeated a spirited Thailand 3-1 on Saturday.

They will likely battle for the trophy against defending champions China, who are overwhelming favourites to overcome Denmark in the second semi-final later on Saturday.

Ko Sung Hyun was the hero for the 2003 champions, as he secured two points in winning his mixed and men's doubles matches at the Putra Stadium.

He said: "It wasn't easy. The match was very different from that of our group encounter (which South Korea won 5-0). This is the semi-finals and it is definitely harder,"

Ko and Kim Ha Na gave the South Koreans the perfect start when they outplayed former All-England runners-up Sudket Prapakamol and Saralee Thoungthongkam 21-18, 21-19 in only 26 minutes.

Thai veteran Boonsak Ponsana levelled the match when he thrashed an inexperienced Lee Dong Keun 21-9, 21-12.

"It was my game plan to make his life hard. I wanted to move him round the court," said the 31-year-old Boonsak.

It was one-way traffic in the next two matches. Ko and Lee Yong Dae made it 2-1 for South Korea with a comprehensive 21-12, 21-11 victory over Maneepong Jongjit and Nipitphon Puangpuapech.

Sung Ji Hyun then outplayed former world junior champion Ratchanok Inthanon 21-17, 21-14 to clinch victory for the Koreans against the Thais, who were playing in their first ever Sudirman Cup semi-final.

South Korea won the Sudirman Cup in 1991, 1993 and 2003 and last reached the final in 2009.