In this paper, a compact and effective implementation of physical theory of diffraction (PTD) formulation is proposed. The PTD formulation is tailored to recently developed high-frequency radar cross section (RCS) prediction tool; Predics. This PTD implementation is unique such a way that it is specially tailored to shooting and bouncing ray (SBR) technique via ray tracing and field tracing techniques. The detailed derivation of this PTD implementation is formulated and the algorithm steps are given together with its inclusion to Predics. The success and the validity of the proposed PTD implementation to the ray-launching RCS simulator have been tested with several benchmark targets that have either analytical or measured RCS values. Simulated RCS results ensure the accuracy of the proposed diffraction formulation that has been attached to the SBR technique over the test targets given within the paper. To better assess the effect of diffraction phenomenon to the total RCS value, more realistic targets; namely a missile and a helicopter target are analyzed by comparing the RCS results with and without PTD contributions.