This study investigates how child skills, parental investments, and the school environment influence early childhood development in the context of rural Thailand. Using data from the Reducing Inequality through Early Childhood Education (RIECE) program, our findings suggest that a child’s lagged cognitive ability leads to improved language (expressive and receptive) and gross motor skills. Relating to parental investments, time investment is important for fine motor skills, receptive language, and personal-social skills. In contrast, material investment is only significantly linked to improvements in expressive language. Schooling intervention through the RIECE curriculum improved gross motor skills as well as expressive and receptive language skills. Finally, teacher experience led to better fine motor skills, while a higher student teacher ratio improved expressive language skills. Our findings are heterogeneous across child genders.