  We explore the simplest viable dark matter model with a real singlet scalar,
vector-like singlet and doublet fermions. The Yukawa couplings associated with
the fermion sector play a crucial role in getting the current relic density
through Freeze-in and Freeze-out mechanism. We discuss the constraints from the
recent muon anomalous magnetic moment experimental data and relic density. We
also perform the collider analysis for the FIMP dark matter in the context of
14 TeV LHC experiments with the MATHUSLA100/200 detector. Our analysis shows
that one can get enough events $>3$ for heavy charged fermion track at 14 TeV
LHC with an integrated luminosity $\mathcal{L}=10^6 ~{\rm fb^{-1}}$.
