The effects of the peculiar in-plane lattice vibrations in monolayer molybdenum disulfide (MoS2) are oftentimes ignored in the analysis of the material's lattice behaviors due to the lack of variation of polarization for the excitation light. In this work, we have observed variations in the relative intensity of the two most dominant Raman peaks of MoS2 via polarized micro-Raman spectroscopy using elliptically polarized incident light. The asymmetry of the incident excitation light gives an additional degree of freedom affecting the relationship between the x- (E12gx) and y- (E12gy) components of the material's in-plane lattice vibrations. Different ratio of the magnitudes for E12gx and E12gy in the lattice vibrations can be induced by changing the polarization state of the incident light. This work investigates the material's unexplored fundamental phonon property which may enlighten past and future studies involving phonon behaviors.