Yabba, ie crystal meth mixed with additives, is indeed a scourge, especially, but not exclusively, in Isaan. It is a stimulant that results in extreme aggression, doubly so if combined with alcohol. It is cheap and readily available. The police should be incentivised to be more active in helping to control it's use. A further thought, if users can't exist without some form of restorative cannabis would be a much less harmful alternative.