Health assembly is one of a mechanism in the process of Thai Health System Reform which is an ambitious movement for total change of Thai health system fromideology to practices; from individual, community, and professional levels, to national level. Assembly is a new mechanism for public participation Thailand. This mechanism aims to bring multi-sectoral cooperation to promote new health system that emphasizes prevention rather than curative health where by the term ‘health’ was defined in a broader term included various aspects of well-being which beyond the realm of medicine. First movement of the health system reform is to launch the “National Health Bill,” that will be a new Thai health constitution, a guarantee for new health system to exist and maintain people participation. The National Health Reform Committee and the National Health System Reform Office, thus, form an ad-hoc committee to mobilize and organize health assemblies in almost 500 districts, 75 provinces, and one national assembly. The ideology behind organizing health assembly is to consider these assemblies as “social innovation” for people participation in the policy making and legislation procedure. Therefore, each sub-committee at all level is allowed to create different procedures to make people participated in this law making procedure as much as possible. The procedures are expected to be acceptable to local cultures and settings. The assemblies, thus, need not be formal, or totally informal; whatever types or forms of social gathering for this purpose is achieved there would be lesson learn to other assemblies that followed. Thus, the provincial health assemblies were organized according to local setting, which in turn gave lesson to the national health assembly. Every procedure is differed depend upon various factors. This study, therefore aims to document and analyze the procedures of the assemblies to see what the primary forces that bringing people participations in different kind of settings. It also aims at understanding the whole picture of people interaction in different kind of stage arrangements. This report also analyze the procedures of health assemblies as a form of social process that scrutinize, on the one hand, instrumental components of social transaction, environment, and tools for interactions; and expressive components of social transaction, emotional reaction, symbolic representation, and exchange of ideas and knowledge. The result of this study revealed numbers of factors influencing people participation in the assemblies, particularly the components of multi-sectoral participants which was a challenge to organizers; the nature of moderators and the dynamic of interactions which could enhance or became a barrier for people participation at the same time; the matter of the contents of the discussion which could bring cooperative or protesting atmosphere; and the formats of the meeting which create a pressures or accommodating nature for participation. On the other hand, this research also found that the assembly (particularly national health assembly), reveal a set of political procedure resemble of neo-communitarianism which emphasize on public/civic engagement of an eclectic group of participants. Even though, health is an agreeable subjects that people could easily accepted the ideas of change for the good will of people, health assemblies, emphasize communicative culture of formal talk and discussion with specific set of rules, people who are not familiar with the procedures could found a resistant to some of the subjects discussed by persons of different background. This study is only able to reflect what had happened at the front stage of communication which left the back stage of communication untouched, and to be further study with cooperation of those who organized the assemblies in the future.