By The Nation
The world No8, after losing the second round-robin match of group B to Nozomi Okuhara on Wednesday, put on a masterclass of her all-round game to beat the Canadian at 21-13 21-12 in just 37 minutes.
It was a sweet revenge for Ratchanok, who was eliminated by Li from the All England Open in March.
With two wins in three matches, the Thai No1 finished second in the group behind leader Okuhara.
On Saturday she faces Sindhu V. Pusarla the winner of group A, while Okuhara will face defending champion Akane Yamaguchi, the runner-up of A group.
Other Thais joining joining Ratchanok in the semi-finals were the mixed doubles pair of Dechapol Puavaranukroh and Sapsiree Taeratanachai.
They lost their last group A round-robin match to Zheng Siwei and Huang Yaqiong 21-9 21-8 but had already booked their semi-final spot by clinching second place to the Chinese pair, thanks to a win on Thursday over the British pair Marcus Ellis and Lauren Smith of Greta Britain.
In women's doubles, Jongkolphan Kititharakul and Rawinda Prajongjai were knocked out of the tournament after losing to Japanese Mayu Matsumoto and Wakana Nagahara 5-21 12-21.