A body A rests on a railway platform while an identical body B is...

Body $A$ is at rest on the ground, so its macroscopic velocity $v_A = 0$.

Body $B$ is in a moving train, so its macroscopic velocity $v_B > 0$ with respect to the ground.

Kinetic energy of $A$ is zero, while kinetic energy of $B$ is $\dfrac{1}{2}mv_B^2 > 0$. Thus, the kinetic energy of $B$ exceeds that of $A$.

Mechanical energy is the sum of kinetic and potential energy. Assuming both bodies are at the same reference level, their potential energies are equal. Hence, the mechanical energy of $B$ is greater than that of $A$.

Internal energy depends only on the internal state (temperature, molecular arrangement) of the body and is independent of the macroscopic frame of reference. Since $A$ and $B$ are identical, their internal energies are equal.

Total energy is the sum of mechanical energy and internal energy. Since the mechanical energy of $B$ is greater and internal energies are equal, the total energy of $B$ exceeds that of $A$.