World number 24 Sindhu, who is the lone Indian woman in fray at the event in the absence of star compatriot Saina Nehwal, won 10-21 21-7 21-19 in a 47-minute contest against the world number 14 Thai.
The 17-year-old Sindhu will now face second seed Li Xuerui of China in the last-eight stage tomorrow.
Gurusaidutt also notched up a come-from-behind win against Kashyap, who was seeded eighth in the event. The lower-ranked of the two Indians prevailed 16-21 21-18 21-4 after slogging it out for an hour and six minutes.
A tougher challenge awaits him in the quarters where he will be up against top seed Chinese Chen Long.
Meanwhile, Sourabh Verma and Ajay Jayaram set up a clash against each other after winning their second-round matches.
While Sourabh triumphed 21-12 21-16 against Chinese Taipei's Jen Hao Hsu, Ajay defeated Singapore's Zi Liang Derek Wong 21-17 21-9. Both the Indians took less than an hour to register their respective wins.
But there was disappointment for India in the doubles arena where eighth seeds Ashwini Ponnappa and Tarun Kona crashed out of the mixed event in the opening round itself. The Indians lost 9-21 14-21 to the Malaysian combination of Jian Guo Ong and Yin Loo Lim.
