Bagging his second National Billiards title, he won his maiden crown in 2014, Kothari started with a bang to win four straight frames in the best-of-nine frame (150-up each) summit clash.
The former Asian Billiards champion had three 100-plus breaks in the first four frames to unsettle Parekh, who was playing his first National Billiards final.
"I am just over the moon. I had spoken to dad (Manoj Kothari - National cuesport coach). He told me a few things and that really helped," Sourav told PTI.
"It was a tough match regardless of the scoreline. Especially, the way Siddharth was playing I knew I had to start off well. I mean 0-4 down he came back with two century breaks. So a great match and great finish for me," added a jubiliant Sourav.
The finalists have also booked their berth for the Asian Billiards in Colombo starting March 1.