This research was conducted to study the development of senator acquisition models, to compare them with other countries, to study factors influencing the success of the model and method of acquisition of senators in Thailand, and to develop a model of acquisition of senators suitable for Thailand. This research work is conducted by collecting data from interviews with 14 informants, 2 focus group discussions, and a questionnaire survey of 645 respondents, for analysis. The results from the research are as follows.
1) The development of the model of the acquisition of Thai senators begun with the appointment and change to all elected senators according to the 1997 Constitution, but there was a problem of interference from political influence. Thus, the method was changed to some elected senators and some appointed senators, but there were problems in performing duties. However, there were problems of the origin of power. Thus, the 2017 Constitution changed so that all senators are appointed. .
2) As for the models for senator acquisition for the United States, France, Japan and Malaysia, it has been found that the models can be divided into two models, namely, elected senators, namely the United States, France, Japan, and as for England and Malaysia, the method is the appointment. The model of election or appointment will have different details in each country.
3) From the study of factors influencing the success of the model of senator acquisition in Thailand, it was found to consist of three factors, namely, the candidate factor, which is especially related to the freedom from the domination by the political party, the factor of the process for obtaining senators which is the participation of the people, and the factor related to the people, the important aspect of which is readiness in terms of knowledge and understanding about senators.
4) As for the development of the model for senator acquisition suitable for Thailand, it has been found that roles and duties of senator are in accordance with the 2017 Constitution, and the feasible approach was used for nomination of senator, but there were additional issues added: 1) the nomination model by the senator selection committee that is relevant to the people; 2) the selection among themselves within the expertise group instead of cross-selection; and 3) the consideration of the group of experts suitable for Thai society.