  We examine the thermodynamic behavior of a static neutral regular
(non-singular) black hole enclosed in a finite isothermal cavity. The cavity
enclosure helps us investigate black hole systems in a canonical or a grand
canonical ensemble. Here we demonstrate the derivation of the reduced action
for the general metric of a regular black hole in a cavity by considering a
canonical ensemble. The new expression of the action contains quantum
corrections at short distances and concludes to the action of a singular black
hole in a cavity at large distances. We apply this formalism to the
noncommutative Schwarzschild black hole, in order to study the phase structure
of the system. We conclude to a possible small/large stable regular black hole
transition inside the cavity that exists neither at the system of a classical
Schwarzschild black hole in a cavity, nor at the asymptotically flat regular
black hole without the cavity. This phase transition seems to be similar with
the liquid/gas transition of a Van der Waals gas.
