I had earlier applied for an adsense account for a domain, but it was disapproved because there was not sufficient content on it. However, now I don't want to adsense on that domain. Instead I have another domain on which I want to use adsense. But when I login into the adsense, it asks me to just resubmit the old request, and not allow to change the site url. Is there any way I request the old request and request for a new site account?
Either contact AdSense support or register using a new email address
It might take a long time to get a reply from adsense support. Instead just try to add more content to your original website, even if you don't want adsense there. You only need it to get the approval. Immediately after you get the approval, you can restore the old site to its original condition and put adsense on your new site.