[rdp] Can RDP clients launch remote applications and not desktops

At least on 2008R2 if the accounts are only used for RDP and not for local logins then you can set this on a per-account basis. That should work for thin clients. If the accounts are also used on local desktops then this would also affect those logins.

In ADUsers&Computers, open the properties for the account and go to the Environment tab. On that tab, check "Start the following program at logon" and specify the path and executable for the program.