It seems that many schools in Thailand follow the pattern of asking you not to leave the premises in between lessons, even if you have huge free periods such as three hours or more during the day. They say you should use it for planning. However, I find that the environment is not always the best for planning and I like to organise my own time and planning when it suits me.
There is an irrational, feudal style loyalty model of being where the boss wants you, regardless, yet as some teachers have said, it is flouted in more roundabout ways and, yes - if you want to get away with it, never be confrontational (opposite of union style). Whoever says go to Vietnam and sample a better mode is right. You don't need all the extra 'padding' and really it's about obedience and qualities which aren't ideally suited to teaching or lecturing as a profession.