I believe what you’re talking about is Sin Sod. The man pays money, gold, diamonds, water buffalo etc to the mother of the bride. If the lady is young, never married no kids extremely pretty then her Mom will expect a large amount. If the guy can’t come up with it then the girl won’t marry or see him again.
If the lady has been married before older, has kids then the amount of sin sod is a lot lower.
But I have seen Sid over 10 million baht and 30-50 baht gold.