GOLD COAST - Three-time champions South Korea beat Thailand 3-1 to reach the final of the mixed teams Sudirman Cup at Australia's Gold Coast on Saturday.

The South Koreans downed the Thais with a clutch of teenage players in the absence of their biggest names and will face either defending champions China or Japan in Sunday's final.

Sung Ji Hyun defeated Ratchanok Intanon in the fourth match of the semi-final tie 21-13, 21-17 to clinch passage to the final for South Korea. For Sung it was a battle to prove herself as she admitted she had often faltered in crunch semi-final and final matches.

Dechapol Puavaranukroh and Sapsiree Taerattanachai gave the Thais the opening match winning their mixed doubles, 21-16, 21-12 against Choi Solgyu and Chae Yoo Jung in 41 minutes.

All the pressure was on Korea's men's singles spearhead Son Wan Ho, but he came through to overcome Suppanyu Avihingsanon, 18-21, 21-10, 21-17. "My legs felt heavy because of the matches I played this week," Son said.

"I felt tired in the first game, but knew I had to win. I've beaten him five times before, but in February it went to three games. Today it was the semi-final and I was under greater pressure. He is an attacking player, I had to focus on my defence and cut down on my errors."

Choi Solgyu and Seo Seung Jae were too strong for a deflated Dechapol Puavaranukroh and Bodin Isara in the men's doubles 21-13, 21-16 leaving it all on Ratchanok Intanon in the women's singles to keep Thailand alive in the tie's fourth match.

The Thai however was way below her best, unable to stick in the rallies that Sung forced her into. "It is just amazing," South Korean head coach Kang Kyung Jin said.

"We've made history. This year our team was called weak. At the last minute our senior men's doubles players left the team. We targeted the quarter-final. Now we are so happy. The last two years have not been good for Korean badminton. Now we're trying to set up a new generation and looking ahead at the Tokyo 2020 Olympics."