Agriculture is usually the largest economic sector in developing countries. Typically, most of the countries' population is employed in this sector. The economic growth is dependent upon productivity in agricultural production and its export potential. Increased production and exports from this sector result in foreign exchange earning by which to promote development of the other sectors. Given the importance of agricultural development, this thesis attempts to study the impact of the agricultural sector on Thai economy and to examine some problems concerned with cultivation, production and marketing. The study also concentrates on the development of social overhead capital (i.e., transportation and irrigation systems), which play an important role in stimulating the growth of Thai agriculture. Finally, there are some conclusions and recommendations which may be useful to the government and its agencies concerned with the development of agriculture.