This is a quantitative research focus on family business. The family business has become
internationally interesting topic. Several research papers investigate the impact of family influence,
stewardship leader on business performances. Many family business research papers were done in
developed countries, on the other hand only a few study was done in developing countries. This study
intended to explore the family influence in family business in Thailand, and stewardship leader in family
business in Thailand. Further, this study could help to advance the development of the family firm
theory. In addition, the study developed the model of how family influence could lead to better business
performance, how family influence could bring stewardship leader, and stewardship leader could also
lead to increase business performance. The study seeks to expand the scholar of doing research in the
family business field in Thailand. The data were collected in Thailand, from 400 small and medium size
family businesses in Thailand. A list of family businesses was generated from various source, includes
Family business Research Center of the University of the Thai Chamber of Commerce. The primary data
was collected through questionnaire sent to the family business companies under study. The structural
educational model (SEM) via Lisrel program was used to analyze the data. The result of the study
showed the significant positive relationship between Family influence and business performance, family
influence and stewardship leader, as well as the relationship between stewardship leader and business
performance