Family almost always comes first in Thailand, with a much greater emphasis placed on the extended family than it typically is in western countries. If you’re shocked by the number of siblings a Thai person has, it’s highly likely many of those are cousins—there’s no word in Thai for cousin and people refer to cousins as their brothers and sisters.
It’s normal for extended families to live close to each other, with many Thais maintaining strong links with their home villages even if they move away for work. It’s fairly common for children to be raised by grandparents or aunts and uncles if their parents need to work elsewhere, such is the role of extended family in everyday life. Younger members of the family are expected to help take care of older members. This can be financially, or by doing a range of chores.