  A theoretical description of the differential decay spectrum for the decay
tau- -> nu_tau K_S pi-, which is based on the contributing K pi vector and
scalar form factors F_+^{K pi}(s) and F_0^{K pi}(s) being calculated in the
framework of resonance chiral theory (R$\chi$T), additionally imposing
constraints from dispersion relations as well as short distance QCD, provides a
good representation of a recent measurement of the spectrum by the Belle
collaboration. Our fit allows to deduce the total branching fraction B[tau- ->
nu_tau K_S pi-] = 0.427 +- 0.024 % by integrating the spectrum, as well as the
K^* resonance parameters M_{K^*} = 895.3 +- 0.2 MeV and Gamma_{K^*} = 47.5 +-
0.4 MeV, where the last two errors are statistical only. From our fits, we
confirm that the scalar form factor F_0^{K pi}(s) is required to provide a good
description, but we were unable to further constrain this contribution.
Finally, from our results for the vector form factor F_+^{K pi}(s), we update
the corresponding slope and curvature parameters lambda'_+ = (25.2 +-
0.3)*10^{-3} and lambda''_+ = (12.9 +- 0.3)*10^{-4}, respectively.
