I don't know if this is a configuration option or not.
If I have Firefox open it's on the left of the task bar. If I use a Thunar shorcut (desktop or panel), Thunar opens but the panel shows Thunar to the left of Firefox.
Historically new programs open to the right of older ones. I'm guessing this is still true as Thunar is starting at login for the trash service? How can I start a new process or at least get the panel to see a new event from Thunar? It's just confusing me, not exactly a bug. :-)
TIP: Proofread carefully to see if you any words out.