The world No 40 Khosit came back from the opening game deficit to beat Indonesian Shesar Hiren Rhustavito 19-21 21-13 21-7 while Thai No 3 Suppanyu Avihingsanon, seeded 10th, also had to dig deep to beat fellow countryman Sitthikom Thammasin 10-21 21-19 21-16.
Khosit next plays Kodai Naraoka of Japan whom he beat 21-15 21-14 in Osaka Challenge in March. Suppanyu faces Goh Giap Chin of Malaysia.
In the women’s doubles, Chayanit Chaladchalam and Phataimas Muenwong also reached the semi-finals and will take on Indonesian eight seed Anggia Shitta Awanda and Yulfira Barkah today.