Only a few years back, Thapar University considered admissions on the basis of the JEE Mains scores and the cut-off ranged around 190 for students of the general category, and almost around 150 for students who were either from the Sc or ST category. 

In 2017, Thapar University only took admissions on the basis of the JEE Mains rank, and it ranged around 20,000. The required cutoff percentile for CSE is 85.72, according to the recent cutoff trends.

You might secure admission in the COE branch if your rank is somewhat around or slightly over 100. Other than that, you always have the option to opt for a branch change (upgradation). 

You should research more about the SC and ST categories on the main website since it varies every year.