ถ Executive Summary Equality Principle was recognized by international human rights instruments and foreign laws. However, “Discrimination” which comprises of two important factors i.e. “Ground of Discrimination” such as gender, race, religious etc. and “Area of Discrimination” such as employment, education, good and service etc., could be regarded as an obstacle to achieve equality. However, the main problem of this research was to study whether the existing laws of Thailand has sufficiently covered practices relating to discrimination. This research used qualitative method and conducted comparative analysis with international human rights laws, foreign laws including laws of the EU, South Africa, Sweden, Finland, Canada, Australia, Singapore, Malaysia, India and the U.S. The results indicated that the legal meaning and scope of “Discrimination” varied depending on different dimensions and contexts. The main results of this research could be summarized as follows; Regarding Equality Principle, the research found, by comparing foreign laws, that the constitutional structure relating to the protection of equality ere are 3 models; the first one classified equality as “general equality”, “specific equality” and “non-discrimination”. The second model divided only two principles, i.e. “equality” and “non-discrimination”. The third one only identified “non-discrimination”. According to Thai Constitution and related Act, “Unfair Discrimination” was stipulated leading to the question whether such term is consistent to international humanitarian laws. The results indicated that foreign laws shared similar principle in classifying between “distinction of treatment that is prohibited” and the “distinction of treatment that is not prohibited”, however, the pattern of using this term can be categorized in 4 models, (1) categorizing “Unfair Discrimination” and “Fair Discrimination”, (2) categorizing “Unlawful Discrimination” and “Lawful Discrimination”, (3) categorizing “Discriminatory Practice” and “Non-Discriminatory Practice”, (4) categorizing “Differential Treatment” or “Distinction of Treatment” and “Discrimination” without using the “Fair or Unfair” element. In this regards, Thailand can be classified in the first model. However, constitution provided no clear definition of “Unfair” Discrimination. Thus, Court interpretation played vital roles in providing scope and meaning of such term. In addition, this research found, by comparing to international laws, that there is no element of “Fair or Unfair” because the differential treatment that was not fall under the scope of “Discrimination” was termed merely “Differential Treatment or Distinction of Treatment”.