Thailand booked two double rooms, one with an extra bed for three adults and one with two large rooms and one small room, but a friend suddenly wanted to go, and there was no room in the hotel.

You are not allowed to live with three adults and one child. There are three adults in the other room. Why can't the other adult stay with her in a nearby hotel for one night? At the same time, communicate with the hotel to see if there is a room for the next day. If not, stay with her. There is nothing inconvenient.

The extra bed fee can't be wasted. You can try to communicate, but the hotel is unlikely to refund this money.