Greetings dear aspirant

The cut-off trends keeps changing every year and it depends on the number of students attempting the exam, difficulty level, number of available seats, etc. With marks of 156, you cannot secure a CSE seat in Sri Sivasubramaniya Nadar (SSN) College of Engineering in Kalavakkam as the opening marks for CSE brach was 166 and the closing marks was 199 in TNEA previous few years. So, just apply to their counselling process and try for other colleges.

https://www.careers360.com/colleges/sri-sivasubramaniya-nadar-college-of-engineering-kalavakkam/cut-off

You can have a look at the detailed glance about everything related to SSN previous year cut-off trends from the above link.

Hope I've cleared all your doubts!!

All the best for your future career