Starting from the Rabi Hamiltonian, which is useful to get non-perturbative results within the rotating wave approximation, we have obtained the Einstein's B coefficient to be time-dependent, B(t) ∝ |J0(ωγ t)|, for a two-level system (atom or molecule) in the thermal radiation field. Here ωγ is the corresponding Rabi flopping (angular) frequency and J0 is the zeroth order Bessel function of the first kind. The resulting oscillations in the B coefficient -even in the limit of very small ωγ -drives the system away from the thermodynamic equilibrium at any finite temperature in contrary to Einstein's prediction. The time-dependent generalized B coefficient facilitates a path to go beyond the Pauli's formalism of non-equilibrium statistical mechanics involving the quantum statistical Boltzmann (master) equation. We have obtained the entropy production of the two-level system, in this context, by revising Einstein's rate equations considering the A coefficient to be the original time-independent one and B coefficient to be the time-dependent one.