  Solving the Kadanoff-Baym (KB) equations in a different method from our
previous analysis, we obtain the CP violating parameter $\varepsilon$ in the
thermal resonant leptogenesis without assuming smallness of the off-diagonal
Yukawa couplings. For that purpose, we first derive a kinetic equation for
density matrix of RH neutrinos with almost degenerate masses $M_i \ (i=1,2)
\sim M$. If the deviation from thermal equilibrium is small, the differential
equation is reduced to a linear algebraic equation and the density matrix can
be solved explicitly in terms of the time variation of (local) equilibrium
distribution function. The obtained CP-violating parameter $\varepsilon_i$ is
proportional to an enhancement factor $(M^{2}_{i}-M^{2}_{j}) M_i \Gamma_j/
((M^{2}_{i}-M^{2}_{j})^2 +R_{ij}^2)$ with a regulator $R_{ij}=M (\Gamma_i +
\Gamma_j)$, consistent with the previous analysis. The decay width can be
determined systematically by the 1PI self-energy of the RH neutrinos in the 2PI
formalism.
