Spatial concentration of manufacturing always ends up with regional inequalities. This phenomenon is also true in the case of Thailand. The pattern of industrial development in Thailand from 1996 to 2005 was examined using composite index in analyzing the pattern, the results of which are described in this paper. The review was aimed at assessing the effects of development policies and the factors that influenced the concentration of industrial development in the country. Results of the analysis indicated that most industries are concentrated only in Bangkok and its vicinity even if the Government of Thailand has promoted investment policies to support and develop provincial industries in the remote rural areas. Moreover, the results also showed that capital intensive based industries are concentrated in the urban areas, while the resources-based industries are mainly found in the rural areas. Despite wide zonal variation of industrial development within Thailand, the outcomes of the industrial decentralization policy are very impressive and leading to the path of greater success in coming decades.