Selective Laser Sintering (SLS) is the most common type of Additive Manufacturing (AM) process using granular materials which has the potential to revolutionize the manufacturing industry. However, in the layer-wise build-up of the three-dimensional specimen, the complex laser-material interactions and the poor selection of associated process parameters can give rise to an increase to a number of defects of the artifacts. In fact, the temperature distribution along the surface and in depth at the laser spot, which are strongly affected by the thermal conductivity of the powder bed, do affect the hatch distance and the thickness of the powder layer, as well as on the quality of the final artifact. In this study, a laser sintering experimental set-up, equipped with an Infra-red thermographic camera and a K-type thermocouple, is built to measure the temperature distribution at the surface and 1mm below the surface in a special Polyamide 12 (PA12) powder bed. A one-watt stationary diode laser is used as heat source on samples characterized by various particle size distributions (PSD). Using the set-up, an accurate in-situ thermal characterization of the powder bed along with heat distribution study can be performed. Preliminary tests were conducted and the pixelwise temperature profile along the surface and temperature at the depth of 1mm below the surface of the powder bed has been reported. On the basis of the results, it is possible to provide good estimates of the global energy balances on the system, which are essential in evaluating the energy required to optimize the sintering and melting process of the polymeric powders.