This contribution presents measurements at the GOLEM tokamak using a Timepix3 semiconductor pixel detector with a 1 mm thick silicon sensor and 256 × 256 pixels (pixel size: 55 × 55 μm²). The study focuses on its potential to characterize the X-ray emission generated by the runaway electrons (REs). Advantages of the Timepix3 detector include its high dynamic range, the ability to easily identify detected particles, and the capability to provide spatial position information. The latter can be further exploited by using the detector in a configuration of a Compton camera. To extend the energy range to lower energies (5 - 20 keV), a beryllium window was installed on the tokamak. The measured data obtained by the Timepix3 detector are compared with the results from scintillation probes. This comparison with scintillation detectors includes an analysis of the time evolution of the average and maximum energy of REs. These initial results demonstrate the potential of the Timepix3 detector for advanced diagnostic applications in REs studies.