We observe evidence for $CP$ violation in the decay ${D}^{+}\ensuremath{\rightarrow}{K}_{S}^{0}{\ensuremath{\pi}}^{+}$ using a data sample with an integrated luminosity of $977\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the Belle detector at the KEKB ${e}^{+}{e}^{\ensuremath{-}}$ asymmetric-energy collider. The $CP$ asymmetry in the decay is measured to be $(\ensuremath{-}0.363\ifmmode\pm\else\textpm\fi{}0.094\ifmmode\pm\else\textpm\fi{}0.067)%$, which is 3.2 standard deviations away from zero, and is consistent with the expected $CP$ violation due to the neutral kaon in the final state.