World No 4 mixed doubles players Dechapol Puavaranukroh and Sapsiree Taerattanachai led Thailand to a good start with a straight game win over Seo Seung Jae and Chae Yujung 21-18 21-18.
Then world No 18 Kantaphon Wancharoen extended the Thai lead to 2-0 after he powered past Heo Kwang Hee 21-17 21-17 in men’s singles.
But South Korea struck back in the men’s doubles when Min Hyuk Kang and Kim Won Ho bounced back from the first game deficit to beat Tinn Isriyanet and Kittinupong Kerden 19-21 21-17 21-14.
Former world champion Ratchanok Intanon nailed the coffin for South Korea by defeating New Zealand Open champion Se Young An 21-15 21-17.
The Kingdom also reached this stage in 2017 and 2013 which still remain their best results in the world mixed team competition. They will play China on Saturday.