Gst for small hostel/Hotel

I run a small hostel with 4 rooms in a small town. I have Ac and Non Ac rooms. The Ac rooms are charged Rs.1800 per night. But my annual turnover is less that 20 lakhs. Do I need to take a GST registration or can I just mention that it is income genetrated from other source in the Income tax? I sometimes use booking.com to take bookings for the room. I don't use Makemytrip.com, yatra.com etc