It is well known that formal verification of a large railway signalling system encounters the state explosion problem. To alleviate the problem, researchers usually concentrate on only route interlocking and abstract away other properties. Besides the route interlocking, there are also other vital properties to which failure to comply could potentially lead to danger. According to our experience, most of train accidents often involve human error and errors in other properties rather than errors in the route interlocking. Thus, we encounter a dilemma between fully automated validation of an incomplete model or partial validation of a complete model. We argue that formally modelling the complete model will be more valuable for the on-going projects of the State Railway of Thailand (SRT) because it provides insights and can be used to train new signal engineers. This paper focuses on the complete Coloured Petri Net model of a typical Thai railway signalling system: a double-line station with one passing loop. The model includes train movements that can be simulated and graphically visualized. According to SRT’s signalling principles, we have identified nine properties: route interlocking, alternative overlap, flank protection, aspect sequence, approach signal release, approach lock, back lock, sectional route release and quick route release. Lessons learnt from using CPN Tools to model and validate the railway signalling systems are also discussed.