Phetthong พีรวัสดิ์, and Ruangmontri กาญจน์. 2020. “DEVELOPING GUIDELINES TO ENHANCE COMPETENCY OF TEACHERS IN SELF – DEVELOPMENT ROI – ET PRIMARY EDUCATIONAL SERVICE AREA OFFICE 1”. Journal of MCU Nakhondhat 7 (8). Nakhon Si Thammarat, Thailand:204-17. https://so03.tci-thaijo.org/index.php/JMND/article/view/246257.