Measurement of the branching fractions of the decays $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{K}^{+}$, $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{\pi }^{+}$, and $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}^{*+}$

Studies are performed of the Cabibbo-favored decay $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{K}^{+}$ and the singly Cabibbo-suppressed decay $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{\pi }^{+}$, based on a sample of $ {e}^{+}{e}^{-}$ collision data, corresponding to an integrated luminosity of $ 4.5\text{}\text{}{\mathrm{fb}}^{-1}$, accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector. The decay $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{\pi }^{+}$ is observed for the first time. The branching fractions of $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{K}^{+}$ and $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{\pi }^{+}$ are measured to be $ (3.04\pm 0.30\pm 0.16)\times {10}^{-3}$ and $ (1.73\pm 0.27\pm 0.10)\times {10}^{-3}$, respectively, where the first uncertainties are statistical and the second are systematic. These results correspond to the most precise measurement of these quantities for both decays. Evidence of a $ {K}^{*+}$ contribution in the $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}_{S}^{0}{\pi }^{+}$ decay is found with a statistical significance of $ 4.71\sigma $. The branching fraction of $ {\mathrm{\Lambda }}_{c}^{+}\to \mathrm{\Lambda }{K}^{*+}$ is calculated under three possible interference scenarios, with the significance increasing to $ 5.03\sigma $ when interference is taken into account.