Improving educational quality at the primary level is a major goal of Thailand's sixth 5-year Education Development Plan (1987-91). There is a special commitment to improve quality in rural areas and among economically disadvantaged groups, handicapped children, and linguistic minorities. Inservice education is one vehicle for training teachers to meet changing demands wrought by national development goals, technological advancements, and new societal values. This paper focuses on two exemplary inservice programs since 1980. Specifically, the paper discusses: types of inservice activity since 1980, their effects on closing the gap between urban and rural student performance, the influence of U.S. inservice programs, and the applicability of Thailand's experience to other developing countries. Three criteria frame the discussion: locus of control, instructional delivery mode, and use of a research base. The Improvement of Teaching Efficiency of the Primary School Teachers and The Principals' Inservice Program represent major attempts to upgrade teacher and principal competency since 1980. Several conditions influenced program success, including: the use of self-instructional materials, a school-based locus of control, and a collaborative, collegial ambience. Thailand's inservice experience provides lessons for other developing countries regarding the program's reliance on self-instruction, research, and pre-implementation training and its emphasis on the principal's central role in influencing learning climate. An effective inservice program can minimize disparities in teacher competency. (27 references) (MLH)