The objectives of this research were to study the development of a curriculum for enhancing grade 9 students' cognitive skills using a curriculum based on Systems Thinking Process. There were 3 phases: 1) studying of the problem; 2) development of tentative curriculum; and 3) implementation of the curriculum in a pilot study. The samples were 32 students studying in Ban Phon Kroke School. The statistics used for data analysis included Percentage, Mean, Standard Deviation, Content Analysis and F-test. The research findings showed that the students were competent in using the Systems Thinking Process. Particularly, every student was able to determine the problem, specify variables relating to the problem, write a chart indicating behavioral pattern relating to the problem as well as causal cycle chart, present the thinking process outcomes, evaluate thinking process, and reflect the correct ways of thinking. The comparative findings of competency in using the Systems Thinking Process showed that the students had a higher posttest competency than the pretest at 0.01 level of significance. Additionally, the students said that the curriculum was highly appropriate. A longer period of follow up in the curriculum usage should be performed to see whether the students retain this competency and whether their behavior still expresses this competency in Systems Thinking Process.