Objective: To develop a substance literacy scale for Thai population.
Material and Method: The research design was divided into 8 steps as follows: 1) devising the items, 2) exploring construct
validity of each factor, 3) validating reliability of each factor, 4) generating construct validity of scale, 5) testing conceptual
construct of the scale, 6) constructing alternated rating scales, 7) conducting cognitive test, and 8) conducting pilot test. There
were 15 experts involved in the content validation of scale. The research was conducted with 3,824 samples of Thai population
aged between 12-65 years old from all over the country using the Stratified Three Stages Cluster sampling technique.
Results: Two substance literacy scales were developed. A standard has questionnaire of 37 items. The scale content validity index was 0.65, concurrent validity was 0.648. A short has questionnaire of 32 items. The scale content validity index was 0.86, concurrent validity was 0.667.
Conclusion: Both scales are simple and easy to use. Scale characteristics are appropriate to assess the substance literacy of population. It can be beneficial to planners for strategic development to respond to the problem more accurately.

Keywords: Substance literacy, Scale development, Substance, Thai population