This is how to use subdomain for custom domain microsite

Now subdomains can be used in custom domains. This service is only available on the ULTIMATE package. So you can use a subdomain from your original domain to create a custom domain.

Here's how to use a subpage domain. Make sure you are already using a custom domain if you want to use a subpage domain.

Can I use a subdomain on s.id?

To use a custom domain on a microsite at s.id, make sure you have a domain first