Hydrogen storage has become a global challenge for scientists of this era because it is an economical, clean, and non-pollutant element present in nature. In the present work, the DFT study of structural, electronic, optical, and thermoelectric properties of metal hydride XNaH2 (X = K, Rb) has been performed. Both of these materials are found stable in ambient conditions having semiconductor nature. The optical properties have been investigated in terms of dielectric function, refractive index, absorption coefficient, extinction coefficient, optical conductivity, reflectivity, and energy loss function. The better thermoelectric profile of these composites computed from the BoltzTraP2 code to shows their remarkable thermoelectric response between 200 to 950 K temperature. Remarkably, the computational calculations of these hydrides are made, which could lead to outstanding advancements in applications for hydrogen storage.