Today, the fact that THz and mm-waves can be used in many areas of our daily lives reveals the necessity for devices that can efficiently detect these waves. Due to the low energies with respect to ambient conditions, it has been a challenge to develop sensitive, fast detectors using conventional approaches. The plasma medium offers a unique way to detect this radiation. Many conflicting theories have been offered historically on the details of the detection mechanism of the experimentally observed interaction between plasma and THz/mm-wave by using classical analytical approaches. Nevertheless, inexpensive neon glow lamps realized as glow discharge detectors (GDDs) continue to be a region of great interest for the mm-wave and THz community. Here, the nature of the plasma in the glow discharge lamp is investigated for the first time using the particle in cell/Monte Carlo collision (PIC/MCC) method based on a kinetic approach. After obtaining the distribution of the entire glow discharge, its interaction with THz/mm-waves is simulated and compared with experiments. Excellent agreement for the observed changes in current and spatial distribution of the negative glow is further aided by the observed increase in responsivity with increasing modulation frequency, which, to the best of our knowledge, has not been explained before. In this context, the effect of radiation frequency and modulation frequency on this interaction is examined separately, and the situations required for the efficient use of neon indicator lamps as detectors are discussed.