Thailand slipped nine places to 56th in <a href="http://data.worldjusticeproject.org/#table" target="_blank">the 2015 Rule of Law Index global ranking</a>.
The top overall performer was Denmark and the bottom performer was Venezuela.
Among the 15 surveyed East Asia and Pacific countries, Thailand was 11th, ahead of Vietnam (64th), China (71st), Myanmar (92nd) and Cambodia (99th), the survey conducted by the World Justice Project (WJP) shows.
Regionally, the top performer was New Zealand and the bottom performer was Cambodia.
Other Asean founding members fared better. At 9th globally, Singapore led, followed by Malaysia (39th), the Philippines (51st) and Indonesia (52nd), according to the survey, an annual report that measures how the rule of law is experienced by the general public worldwide.
The WJP says its Rule of Law Index, which ranks 102 countries, is the most comprehensive of its kind and the only one to rely on primary data.
The scores are based on responses from 1,000 people in each country, who were asked questions about corruption, basic freedoms, regulation and other governance issues, and on testimonies from local legal experts.
Performance is assessed using 44 indicators across eight categories, each of which is scored and ranked globally and against regional and income peers: constraints on government powers, absence of corruption, open government, fundamental rights, order and security, regulatory enforcement, civil justice, and criminal justice.
In the area of fundamental rights, Thailand is trending lower.