To disable xfce panel and/or Thunar from starting in XFCE:
- Start a clean xfce session with no application started
- Open XFCE settings manager > Session and Startup > Session tab
- Set “Never” in front of xfce4-panel and Thunar
- Click Save Session
- Logout and login again to test
EDIT 2014-04-27: You can also edit
To remove Thunar daemon : Remove the Client3* properties for Thunar, then replace Client4 by Client3 and update the Count property from 5 to 4.
Then restart your session.