I think it is the loneliness. Their parents need to go out to work so The children have no friends to play with.
In another view of the parents have only child in the high-risk. In Thailand children need to take care of them parents. If the only child died, parents would not allow people to adopt when they are older.
แนน
1. An only child may grow up lonely.
2. An only child has no one to grow up with.
3. An only child may get too much pressure from parents, to perform well or excel in school and other activities
4. The parents of an only child tend to be overprotective.
5. An only child may get bored of parental involvement
6. An only child may have a harder time making friends.
7. An only child may be pressure to have children in order to carry on the family name.
8. An only child may become burdened about being the sole caregivers of elderly parents.
9. An only child will never have the experience of having nephews and nieces.