The main food in Thailand is rice. Everyone has eaten it since they were born. But we can't really eat rice alone so we have to have something to go with it. There are many dishes of food to go with rice. Most of them are hot and spicy and that is what Thai food is famous for.
Thai people are used to eating rice with their meal. Most Thai people can't have sandwiches for their meal. They call sandwiches a snack. Also, most Thai people do not sit down to eat a proper meal because they usually eat when they are hungry, especially kids and teenagers. If you know some Thai person, you might hear them say "gin khao yung" every time you meet them. It means "have you eaten yet?" or more precise "have you eaten rice yet?".