It's not clear whether you mean access to the client or access from a particular client to the server, but I would assume the latter.
Microsoft Windows Server Operating System gives access rights on a per-user or per group basis, or on a local machine basis. While it is possible to determine the client type via a script, this is something you would need to develop yourself. You could then conditionally apply policies.
Most thin clients have a device login that can be effectively used in place of the Windows login - so users could log into the device with their own usernames and passwords, but the device would auto-login to the domain with pre-determined credentials. I'm not keen on the idea of saving domain credentials anywhere, so this is not something I would do.
It may suit your needs, but I'm curious as to why your client would want to do this in the first place.
Hope this helps CitrixEngineer@yahoo.co.uk