This study of the growth of SMEs in Thailand is based on data obtained from the Ministry of Industry (MOI) and the Ministry of Labor (MOL). The data are available for firms of all sizes (including those with fewer than 10 workers) and they are available annually. Unfortunately, reliable data are for only two variables: number of establishments and number of workers. Data on production or other factors of production are not available from these sources. Nevertheless, time series data from the above sources are able to provide useful information on the growth of firms by size and other contributions of SMEs to economic development.
The MOI data cover statistics of establishments which register with the Ministry of Industry as required by law. Some micro or cottage industries are exempt from registration. Thus, the number of establishments and employment of these industries from the MOI data could be underestimated. On the other hand, the MOL statistics are estimated from two sources of information. First is an annual survey conducted by the Department of Labor Protection and Welfare, and the survey covers establishments with 10 or more workers. The second is data from monthly inspections of firms of all sizes (including those micro industries with fewer than 10 workers) in all provinces of the Department of Labor Protection and the Department of Labor Safety. The following discussions will be based mainly on the MOL data set because the data cover a longer time series (from 1987 to 1996) than the MOI data. However, the MOI data set will be compared with the MOL1 and the NSO data2 to detect and explain possible discrepancies among the different data sources.