Effect of point defects such as vacancies and interstitials on the work function of beta-Ga2O3 thin films grown by pulsed laser deposition was investigated. Relative change in A(g)(3) and A(g)(6) Raman phonon modes indicated formation of oxygen and gallium vacancy defects. The surface potential mapping of Ga2O3 thin films was performed by Kelvin probe force microscopy. Analytical calculations showed variation in work function with oxygen pressure. The work function values at extreme growth pressure conditions were found to be very high. Hence, Fermi level was pinned at the mid-gap energy in both oxygen-deficient condition and oxygen-rich conditions which is attributed to oxygen and gallium vacancy defects. This mechanism of controlling Fermi level pinning in beta-Ga2O3 paves the way to fabricate high performance electronic devices.