Defining financial irresponsibility by age is just lazy and ineffective. Children under the age of 15 are the responsibility of their parents. Their parents are responsible for careless spending. Go after the parents.
The elderly who have their act together (retired, saved money instead of wasting it, etc) should not be lumped in with the elderly who lack the intellect t manage their own money.
This whole scheme, as usual, lacks any nuance. Lazy lumping together is not particular to Thailand, but we're here, so it matters here.