this paper finds that role-relationship has some impacts to language use and interlocutor's understanding in muang society. For example, in the mixing class room that a teacher allowed student to use kam muangmixing with standard thai in class had show that distance between the teacher and the students are not wide and led to the formal language use. Another relationship between the teacher and the students in municipal school that had influenced to the language use.The teacher corrected the students' language use by using kam muang to explain to the students and also used the word kha which considered as a standard thai word.this showed the politeness which was occurred by teacher-students relationship. This indicates that social role relationship to languages use.