The main purposes of this study are to quantitatively investigate the production structure and the pattern of technical change in Thai agriculture for the period of 1972-94. A translog variable cost function framework is used to estimate a system of the cost function and the associated cost share equations for Thai agriculture. The system is estimated using the iterative seemingly unrelated regression method applied to a panel of 92 observations, comprising annual data from 1972 to 1994 for four regions in Thailand. The analytical results indicate that there were scale economies, low technical progress, and complementarities between capital and fertiliser, capital and hired labour, and capital and unpaid family labour. Technical change was biased toward saving hired labour, operator labour and unpaid family labour and also biased toward using fertiliser and capital.