  We present a detailed spectral analysis of the joint XMM-Newton and NuSTAR
observations of the active galactic nuclei (AGN) in the Seyfert 1.5 Galaxy ESO
362-G18. The broadband ($0.3\mbox{--}79$ keV) spectrum shows the presence of a
power-law continuum with a soft excess below $2$ keV, iron K$\alpha$ emission
($\sim 6.4$ keV), and a Compton hump (peaking at $\sim 20$ keV). We find that
the soft excess can be modeled by two different possible scenarios: a warm
($kT_\mathrm{e}\sim0.2$ keV) and optically thick ($\tau\sim34$) Comptonizing
corona; or with relativistically-blurred reflection off a high-density
($\log{[n_\mathrm{e}/\mathrm{cm}^{-3}]}>18.3$) inner disk. These two models
cannot be easily distinguished solely from their fit statistics. However, the
low temperature ($kT_\mathrm{e}\sim20$ keV) and the thick optical depth
($\tau\sim5$) of the hot corona required by the warm corona scenario are
uncommon for AGNs. We also fit a 'hybrid' model, which includes both disk
reflection and a warm corona. Unsurprisingly, as this is the most complex of
the models considered, this provides the best fit, and more reasonable coronal
parameters. In this case, the majority of the soft excess flux arises in the
warm corona component. However, based on recent simulations of warm coronae, it
is not clear whether such a structure can really exist at the low accretion
rates relevant for ESO 362-G18 ($\dot{m}\sim0.015$). This may therefore argue
in favor of a scenario in which the soft excess is instead dominated by the
relativistic reflection. Based on this model, we find that the data would
require a compact hot corona ($h\sim3\,R_\mathrm{Horizon}$) around a highly
spinning ($a_\star>0.927$) black hole.
