  We realize smooth hybrid inflation in the framework of supersymmetric $SU(5)
\times U(1)_{\chi}\subset SO(10)$ model which provides a natural solution to
the monopole problem appearing in the spontaneous symmetry breaking of $SU(5)$.
The breaking of $U(1)_{\chi}$ symmetry leaves a residual discrete $Z_2$
symmetry, that serves as the MSSM matter parity, realizing the possibility of
the lightest supersymmetric particle as a cold dark matter candidate. The $d =
5$ proton lifetime for the decay $p \rightarrow K^+ \bar{\nu}$, mediated by
color-triplet Higgsinos is found to satisfy current experimental bounds if
split-high scale SUSY scenario is employed. We show that with minimal K\"ahler
potential, the soft supersymmetry breaking terms play a vital r\^ole in
bringing the scalar spectral index $n_s$ within the Planck's latest bounds. In
a minimal K\"ahler potential setup, small values of tensor-to-scalar ratio $r
\lesssim 3.5 \times 10^{-7}$ are obtained, whereas the gravitino mass turns out
to be in the range that favors PeV scale SUSY but is not sufficiently high to
avoid the $d = 5$ proton decay. A non-minimal K\"ahler potential including
higher-order corrections is required to realize successful inflation with
central value of scalar spectral index $n_s = 0.9655$, large tensor modes $r
\lesssim 0.056$ and a low reheat temperature $(3\times 10^{6} \lesssim T_r
\lesssim 6.5 \times 10^7 )$ GeV consistent with leptogenesis and baryogenesis.
