  We investigate non-Gaussianity properties for a set of classical one-mode
states obtained by subtracting photons from a thermal state. Three
distance-type degrees of non-Gaussianity used for these states are shown to
have a monotonic behaviour with respect to their mean photon number. Decaying
of their non-Gaussianity under damping is found to be consistently described by
the distance-type measures considered here. We also compare the dissipative
evolution of non-Gaussianity when starting from $M$-photon-subtracted and
$M$-photon-added thermal states
