This research was to study and compare the role of internal supervision of the administrations of Basic Education in Rayong, Chanthaburi and Trat Provinces by experienced practitioners and the size of the school .The samples used in this study consisted of 358 teachers in Rayong, Chanthaburi and Trat Provinces by random stratified proportionate. The instrument used to collect the data a 5 – rating scale questionnaire. The discrimination was between 0.21 to 0.83 and the reliability was at 0.88. The statistical analysis used were percentage, mean and standard deviation. t-test, and one-way analysis of variance (One - way ANOVA) and Scheffe is method to analyses the data.