Children's subjective well-being is crucial for ensuring decent child development. At present, evidence about children's subjective well-being is limited, particularly regarding insights from developing countries. This study aimed to assess overall life satisfaction, multi-dimensional life satisfaction of Thai pre-teens, and factors associated with the children's overall life satisfaction. A cross-sectional study was carried out with 2277 children in grade 4 to 6 at 50 public primary schools from nine provinces across all regions of Thailand. The data collection took place between September and December 2020. The children were satisfied with their overall life to a considerable degree (8.5 out of 10). Girls had higher life satisfaction and satisfaction with multiple life domains (except for "autonomy") than boys. Compared with older children, younger children had higher overall life satisfaction and satisfaction with multiple life domains except for "autonomy", "yourself" and "friends". The children's overall life satisfaction was increased in proportion to satisfaction with family, friends, oneself, physical appearance, health, teacher, school activity, and autonomy. Concerning individual factors, their social skills and time spent on gardening (≥1 h/day) and active recreational activities (1-3 h/day) had positive influence upon their overall life satisfaction, while too much time on screen (>1 h/day) and music (>3 h/day) had negative results. In terms of family factors, children having fathers owning a shop/business had higher life satisfaction than children having fathers who were manual workers, while children who lost their fathers had lower life satisfaction. For school factors, school connectedness had a positive relationship with their overall life satisfaction. Children's subjective well-being promotion should include family-based and school-based interventions to improve children's time use (e.g., more active outdoor lifestyle and less sedentary lifestyle), self-esteem, health, autonomy, and school connectedness.