'Clean and safe' agricultural products are an important issue among consumers, farmers and governments. Many developing countries develop their produce at various points along the 'clean' continuum based on four different production practices related to use of synthetic chemicals. Organic farming is applied to technologies with no chemicals or synthetic fertilisers used during production or processing. It was initially developed by farmers and non-government organisations in Thailand, and subsequently implemented by the Thai government through a series of policies on clean produce to meet international standards. Safe-use and pesticide-free practices lie between organic and conventional practices, and are possible steps when converting conventional farms to organic farms. The main purpose of this paper is to examine the production efficiency of four different vegetable farming practices. We compare the technical efficiencies and technology gaps of the four farming systems in northern Thailand of which three - organic, pesticide-free and safe-use - are designated 'clean and safe'. Farm-level data on vegetable production were collected from random samples of farms using these technologies. A standard stochastic production frontier was estimated for each system to obtain technical efficiency (TE) estimates with respect to their respective cohorts. The likelihood ratio test indicates that significant technology differences exist between these farming practices. Accordingly, a metafrontier model was estimated, enabling the estimation of technical efficiencies and technology gap ratios (TGRs) for vegetable farms operating under the different production systems. The model was checked for self-selectivity bias and it was found that there was no such problem.