You shouldn't use the
-c switch unless you really are sure of what you are doing. From
Remove all target packages, as well as all packages that depend on one or more target packages. This operation is recursive, and must be used with care since it can remove many potentially needed packages.
You have obviously removed a needed package (or packages). Look back through your
pacman.log and see what packages were removed along with thunar and then reinstall them until you are back at your old set up.
In future, to remove dependencies, use the
Remove each target specified including all of their dependencies, provided that (A) they are not required by other packages; and (B) they were not explicitly installed by the user. This operation is recursive and analogous to a backwards --sync operation, and helps keep a clean system without