  We investigate the effective potential of the $PT$ symmetric $(-g\phi^{4}) $
field theory, perturbatively as well as non-perturbatively. For the
perturbative calculations, we first use normal ordering to obtain the first
order effective potential from which the predicted vacuum condensate vanishes
exponentially as $G\to G^+$ in agreement with previous calculations. For the
higher orders, we employed the invariance of the bare parameters under the
change of the mass scale $t$ to fix the transformed form totally equivalent to
the original theory. The form so obtained up to $G^3$ is new and shows that all
the 1PI amplitudes are perurbative for both $G\ll 1$ and $G\gg 1$ regions. For
the intermediate region, we modified the fractal self-similar resummation
method to have a unique resummation formula for all $G$ values. This unique
formula is necessary because the effective potential is the generating
functional for all the 1PI amplitudes which can be obtained via $\partial^n
E/\partial b^n$ and thus we can obtain an analytic calculation for the 1PI
amplitudes. Again, the resummed from of the effective potential is new and
interpolates the effective potential between the perturbative regions.
Moreover, the resummed effective potential agrees in spirit of previous
calculation concerning bound states.
