  We study exact Wentzel-Kramers-Brillouin analysis (EWKB) for a ${\cal PT}$
symmetric quantum mechanics (QM) defined by the potential that $V_{\cal PT}(x)
= \omega^2 x^2 + g x^{2 K} (i x)^{\varepsilon}$ with $\omega \in {\mathbb
R}_{\ge 0}$, $g \in {\mathbb R}_{>0}$ and $K, \varepsilon \in {\mathbb N}$ to
clarify its perturbative/non-perturbative structure. In our analysis, we mainly
consider the massless cases, i.e., $\omega = 0$, and derive the exact
quantization conditions (QCs) for arbitrary $(K,\varepsilon)$ including all
perturbative/non-perturbative corrections. From the exact QCs, we clarify full
transseries structure of the energy spectra with respect to the inverse energy
level expansion, and then formulate the Gutzwiller trace formula, the spectral
summation form, and the Euclidean path-integral. For the massive cases, i.e.,
$\omega > 0$, we show the fact that, by requiring existence of solution of the
exact QCs, the path of analytic continuation in EWKB is uniquely determined for
a given $N = 2K + \varepsilon$, and in consequence the exact QCs, the energy
spectra, and the three formulas are all perturbative. Similarities to Hermitian
QMs and resurgence are also discussed as additional remarks.
