The National Anti-Corruption Commission (NACC) of Thailand has initiated evidence-based transparency index to measure governance in the public agencies since 2009 as a prevention strategy against corruption in the public sector. In the early stage of instrument development, the evidence-based transparency measurement was conducted by a working group under NACC Research Center. The main objective was to measure the levels of transparency in admininstration of public agencies so that "good practices" could be identified and suggested. Two pilot projects on evidence-based transparency index were conducted in 2010 and 2011. Since 2012, the scope and scale of the project have been expanded by combining perception-based integrity measurement and evidence-based transparency index together, and the assessement of integrity and transparency have involved all types of public agencies nation-wide. The respondents from internal and external stakeholders of relevant public agencies have been included. The Integrity and Transparency Assessment (ITA) project is under an ITA Committee with the Planning and Strategy Division of NACC as the secretariat. The first ITA instrument development was carried out by a taskforce and the ITA project using the developed instruments was commissioned to a university research institute in 2014 Currently, the 2015 ITA instrument are being developed by a working group. ITA is an important and constructive strategy to prevent corruption in the public agencies of Thailand. The ITA measurement is in accord with the UNDP Users' Guide to Measuring Corruption.