It is not true that children in Western countries have complete freedom to make their own decisions. While the children are growing up, parents still make the important decisions about the children's lives, such as what school to go to.
If the children want to go to a party with some friends, often the parents will give permission , but the children must ask first. Most parents won't let their children watch scary movies, or let them listen to music that contains bad language. Many teenagers often try to do these things anyway, and also drink beer or smoke cigarettes, but if the parents find out, they will be punished.
Perhaps compared to Thai culture, western children have more freedom, but the parents are still responsible for their children until the age of 18