With the rapid social and economic development, a great deal of expenditure is crucial for the nation's infrastructure development.� Nevertheless, the governments of many developing nations have been experienced with the limited budget and technical inability to deliver effective public infrastructures.� Public-private partnership (PPP) has been adopted as an alternative collaboration arrangement between the government and the private sector in many nations to overcome these challenges.� PPP can be defined as a long-term contract between a public agency and a private entity for rendering public facilities, including design, construct, finance, operate, and manage the project.� The PPP contract types can be classified by various factors.� Different PPP options imply different levels of responsibility and risks to be assumed by the private operator.� Deciding an appropriate PPP contact type is always a risk-taking task for the government.� This decision-making depends upon several criteria, which directly contribute to project success.� This thesis proposes a multi-criteria decision-making model based on analytical network process (ANP).� The proposed model can be employed to choose a PPP contract type that optimizes important criteria.� The main input of the model is the priorities (weights) of the PPP contracts selection criteria, which are obtained from a series of questionnaire surveys. �The model is applied to four case studies.� One case study is an ongoing project and in-depth interview with a group of PPP experts.� The three case studies are done via online interviews. The outcome of this research is a decision-analysis model that is structured by an analytical network process, which can determine the best type of PPP contract depending on decision-maker's objectives.� This research can assist the stakeholders such as political decision-makers, private investors, and strategic consultants who are responsible for proposing and selecting the various types of available PPP options that will suit their PPP projects.� Moreover, using this supported optimal decision model can minimize the time-consuming of adopting the best form of PPP contract type, and it leads to project success.� Although this proposed model is an innovative approach, due to the limitation of the legal system in Thailand, the proposed model needs to be modified to apply in practice.�