Presented in this paper is a numerical approach to extract useful features of SH guided wave scattering in a Plate-like structure with thickness variation. The problem statement is chosen to establish a physically based guideline for mode selection and data analyses in power industry application. The hybrid BEM technique with absorbing boundaries on the structure cross-sections is proposed to calculate reflection and transmission from thickness variation. Sample numerical data is presented as a function of incident mode, frequency and defect geometry. Mode optimization is proposed to enhance penetration power and quantify geometry change based on various interesting features including reverberation pattern of scattering fields.