A student-teacher ratio expresses the relationship between the number of students enrolled in a school, district, or education system and the number of “full-time equivalent” teachers employed by the school, district, or system. One way to measure teacher’s burden is by using average student to teacher ratio. Obviously, more students per teachers equate to more burden upon the teacher. If a teacher has to look after over too many students, this would impact greatly upon the education provided. For example, secondary school teachers, they have an average of 21 students under their care, which is closer to Laos, Vietnam and Nigeria and worse than countries like Gana, Peru, and China. (Worldbank public data,2008). Teachers do not know the potential of every student in the class because each student based learning inequalities. Students gain knowledge from the teacher has no equal. And what is also important. The ratio of teachers to students is not enough. One teacher has an obligation to teach too much. One teacher taught a variety of subjects Obligations such as school work, engaged in work activities. The reasons of all these teachers have less time to teaching. As a result, test scores, O-net each year fell. Because student-teacher ratios are a general way to measure teacher workloads and resource allocations in public schools, as well as the amount of individual attention a child is likely to receive from teachers, student-teacher ratios are often used as broad indicators of the overall quality of a school. Even though students to teacher ratio cannot completely reflect upon the issues about Thailand’s education, it nevertheless can provide some idea about the burden that Thai teachers have to bear. The discrepancies between primary and secondary also poses an interesting question worthy of pondering what the underlying reason could be and how this would impact negatively or positively upon the nation’s education system.