I can agree with that an assumption that somebody smoking marijuana get aggressive and have hallucinations normally, almost always, will be wrong. However, as most Thais are using this are too young to understand or does not have any knowledge about measurement or the volume they smoke as beginners and not so tolerant to the drug, that will automatically create a possibility. If you smoke far too much marijuana, people can get hallucinations. based on the type of hallucinations a person also can get violent or aggressive. Not a very common thing to happen, but the possibility exists. Mostly a person who gets that kind of reaction also have some kind of psych-problems as well.