An accurate thermodynamic smoothed particle hydrodynamics (SPH) model is developed for multiphase flows with discontinuous thermal and material properties. By introducing a Riemann-based approximation into the SPH heat conduction formulation, the proposed method effectively resolves discontinuities in temperature and thermal diffusivity across phase interfaces, significantly improving accuracy compared with conventional SPH heat transfer schemes. The heat transfer model is consistently coupled with compressible fluid dynamics through the energy equation and appropriate equations of state, enabling the simulation of heat–fluid interaction in multiphase systems. A series of benchmark tests involving one- and two-dimensional heat conduction with strong discontinuities demonstrate improved accuracy and convergence of the proposed method. The model is further applied to bubble dynamics problems, including rising bubbles, bubble coalescence, and oscillating cavitation bubbles. For strongly compressible regimes, thermal conduction and radiation effects are incorporated, yielding good agreement with theoretical solutions and finite-volume results. The present thermodynamic SPH model provides a robust framework for simulating multiphase heat transfer and bubble dynamics under complex thermodynamic conditions.