Because they have a reentry permit, they will likely not be allowed to enter on DTV.
You cannot "switch" visas like that.
As the DTV is not activated, the nonb still is in effect with the reentry permit.
If the work permit is already canceled and you did not cancel the extension, then your reason to stay ended the day you stopped working, you may be subject to a hefty fine.
Should have canceled the extension before leaving Thailand.