Today Thailand is the second largest field crop seed exporter in Asia with maize contributing the highest value to seed exports. Hybrid maize is considerably adopted in Thailand mainly due to the demand from feed industry and development of livestock and poultry industry. The success of varietal development of commercial maize hybrids is owed to the investments of international donors during the 1980s and continuous breeding efforts of multinational seed companies even as public institutions played a key role in maintaining genetic resources conservation and pre-commercial lines research. This paper reviews the history of research and development in maize and maize seed market development in Thailand. Furthermore, expert elicitation method is used to reveal the adoption of commercial maize varieties in 2013/2014 cropping seasons. The results of adopted maize varieties were used to estimate market shares and suggested that maize seed market in Thailand is moderately concentrated with tendencies towards oligopolistic competition.