This paper studies the mixed singular/switching stochastic control problem for a multidimensional diffusion with multiples regimes in a bounded domain. Using probabilistic, partial differential equation (PDE) and penalized techniques, we show that the value function associated with this problem agrees with the solution to a Hamilton-Jacobi-Bellman (HJB) equation. In that way, we see that the regularity of the value function is C 0,1 ∩ W 2,∞ loc . * This study has been funded by the Russian Academic Excellence Project '5-100'.