I once saw this type of thing first hand. I was staying in an Udon Thani MooBan with a GF and her kids. For his birthday, her 7 year old son asked for us to buy ice cream for him and his whole class at lunch. We went to the school headmaster and he said it had to be done through him and asked for B1000 for the ice cream.
On the special day, each kid got about a tablespoon of the cheapest possible ice cream, the kind vendors sell for B10 a scoop. My GF said all in, probably cost him less than B200. The rest went into his pocket.