With the industrialization of Thailand, a lot of young Thai people go to Bangkok to take their chance. They almost continue to send money to support their parents. But parents, far away of children, have less influence on them. Before parents will choose the future mate. Now a lot of young Thai people choose on their own.
Children are the assurance for the parents.
Often Thai children continue to live in their parent's house even if they are old enough to live their own life. Especially for girls, they should not leave their parent's home if they are not married. In Thailand there is no pension when workers retire. So the only support for the old parents are their children. Thai people don't like the westerner principle to send old parents in special nursing-home.