Every child has a younger, called "NONG" or น้อง
When speaking to an elder, Thai children always use the word "PHI" ( พี่ ). When the difference of age is not important, they only use first name. Younger must respect elder, listen to their advice. Elder shall protect younger.
When families visit some Thai friends to present them by their new born baby, the friends may tell the baby is ugly (น่าเกลียด). This is an old Thai tradition in order to fool the evil spirits so that they wander somewhere else.