Ratchanok, world No 11 and eighth seed, on Thursday pummelled the Chinese-born Yao Jie of the Netherlands 21-17 21-10 to next go up against Sung Ji Hyun.
The South Korean Sung last week ushered Ratchanok out in the second round of the All-England Championships to raise her head-to-head record to 4-1 against the Thai teenager. Sung also eliminated three-time world junior champion Ratchanok in the first round of last year’s Swiss Open, before going on to clinch silver.
In the mixed doubles, Thailand are guaranteed a semi-final berth, with third seeds Sudket Prapakamol and Saralee Thoungthongkam due to take on team-mates Maneepong Jongjit and Savitree Amitrapai in a quarter-final late last night.
World No 9 Sudket and Saralee, who captured last year’s India Open, pulled off an exceptional 21-16 21-18 victory over Danes Mads Pieler Kolding and Julie Houmann in the second round, while Maneepong and Savitree came from behind to beat Japan’s Shoji Sato and Shizuka Matsuo 12-21 21-15 21-17.