We propose a model of nodal order parameters for the superconducting A- and B-phase of skutterudite PrOs₄Sb₁₂ and discuss the associated angular-dependent magnetothermal conductivity at low temperatures. The model for the hybrid gap functions Δ(k) containing s- and g-wave parts is consistent with recent thermal-conductivity experiments in PrOs₄Sb₁₂. In particular, the model accounts for the data on the polar and azimuthal field angle dependence of κ_zz(θ,φ). The low-temperature behaviour of thermodynamic properties in zero field is also presented. We show that the effect of impurity scattering on a nodal hybrid gap function immediately leads the opening of a gap and the related exponential behaviour of low-temperature specific heat and thermal conductivity which is very different from d-wave superconductors.