Also topping the qualifying session in their respective categories were Mithun Kumar of Honda Ten10 Racing (Pro-Stock 165cc), Deepak Ravikumar (Super Sport Indian 300-400cc) and Apex Racing Academy's Aishwarya Pissay (Girls, Stock up to 165cc).
Sethu, the 22-year old from Chennai, who has been improving with each outing and is a regular in the FIM Asia Road Racing Championship, clocked the fastest lap of one minute 59.344 seconds.
Championship leader Mathana Kumar (Honda Ten10 Racing) was placed sixth after clocking 02:03.820, behind Prabhu Arunagiri (02:01.842) and S Kannan of TVS Racing (02:03.174).
Bengaluru's Aishwarya Pissay expectedly took the pole position in the girls category ahead of Chennai's Rhyana Bee (Speed Up Racing) and Ann Jennifer.
In the Pro-Stock (up to 165cc) qualifying session, Mithun Kumar, who won both the races in the first round at Coimbatore last month, was the quickest in 02:06.403, followed by Shyam Shankar and Naresh Babu.