  We investigate the prospects for discovering a top quark decaying into one
light Higgs boson ($h^0$) along with a charm quark ($c$) in top quark pair
production at the CERN Large Hadron Collider (LHC) and future hadron colliers.
A general two Higgs doublet model is adopted to study the signature of flavor
changing neutral Higgs (FCNH) interactions with $t \to c h^0$, followed by $h^0
\to WW^* \to \ell^+ \ell^- +\notE_T$, where $h^0$ is the CP-even Higgs boson
and $\notE_T$ stands for missing transverse energy from neutrinos. We study the
discovery potential for this FCNH signal and physics background from dominant
processes with realistic acceptance cuts as well as tagging and mistagging
efficiencies. Promising results are found for the LHC running at 13 TeV and 14
TeV center-of-mass energy as well as future pp colliders at 27 TeV and 100 TeV.
