A first study of CP violation in the decay modes $B^pmto [K^0_{rm S} K^pm pi^mp]_D h^pm$ and $B^pmto [K^0_{rm S} K^mp pi^pm]_D h^pm$, where $h$ labels a $K$ or $pi$ meson and $D$ labels a $D^0$ or $overline{D}^0$ meson, is performed. The analysis uses the LHCb data set collected in $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$. The analysis is sensitive to the CP-violating CKM phase $gamma$ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of $gamma$ using other decay modes.