Costing plays an important role in health economics, particularly economic evaluation. However, there are some controversial issues: concepts, methods and reference values. Hence, it is pivotal to standardize costing methods and use these as national guidelines to produce comparable studies. This report is divided into 3 parts: theoretical issues, international guidelines comparison, and recommendations for the Thai health technology assessment guidelines. Each section is composed of three general costing steps: identification, measuring and valuation. It is recommended to measure economic or opportunity cost mainly in societal perspective. Cost category is composed of direct medical, direct non-medical and indirect costs. The level of reliability of each kind of costing source data is provided. Valuation of resource use based on national standard cost menu is recommended for national policy making. The recommendations on cost measurement are appropriate for the Thai context and in the current situation.