We study the use of a thermal camera as an educational tool for physical phenomena. In particular, we check three factors: surface temperature, emissivity, and external thermal source for more physically accurate use. First, the surface temperature measured using the thermal camera is confirmed by direct comparison with the temperature obtained using a reference thermometer. Second, we demonstrate that using an appropriate emissivity of the target object is significant for accurately measuring the temperature. Finally, the exclusion of an external thermal source is essential for using a thermal camera as an accurate tool in thermal physics. We expect that this study will demonstrate the suitability of thermal cameras as convenient thermometers and the factors required to deliberately consider them in physics classes.