Growth in agricultural production in Thailand can no longer rely mainly on an extension of land area. New technology inputs such as fertilisers, mechanisation, water and chemicals have been adopted. This change has raised questions about the technical change and productivity growth in Thai agricultural production. 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. This results indicate that the availabilities of new land on agricultural production could has the influence on productivity growth in Thailand.