My unused domain redirects to a website I did not set up

My unused domain redirects to a website I did not set up

I bought a domain around 6 months back at namechaeap.com. Didn't host it.

I typed in the domain and saw that it opened some website.

So I tried to use the nameserver of a new hosting service I bought. It still remains the same.

But on further analysis I found that the redirect happens when I do not use www. When I use www it does not redirect (but still returns DNS error). When I use the domain name directly it redirects.

Please help

Domain: thannigaran.com

Without www: without www

With www: with www