To characterize thyroid cancer imaging-based detection, we implemented a simulation of the optical and thermal response in an optical investigation of thyroid cancer. We employed the 3D Monte Carlo method and the bio-heat equation to determine the fluence and temperature distribution via the Molecular Optical Simulation Environment (MOSE) with a Finite element (FE) simulator. The optothermal effect of a neck surface-based source is also compared to a trachea-based source. Results show fluence and temperature distribution in a realistic 3D neck model with both endogenous and hypothetical tissue-specific exogenous contrast agents. It also reveals that the trachea illumination has a factor of ten better absorption and temperature change than the neck-surface illumination, and tumor-specific exogenous contrast agents have a relatively higher absorption and temperature change in the tumors, which could be assistive to clinicians and researchers to improve and better understand the region's response to laser-based diagnosis.