The purposes of this thesis are to study the meanings, categories, virtue and development of the Bodhisatta in Buddhism. The important roles and influences of the Bodhisatta  in the Mekong Sub-Region specifically in Thailand and Lao are also studied. The research was conducted through the documentary research method and the data corrected were analyzed and presented descriptively.

The study found that the word Bodhisatta can be defined as a human being or a being who is dedicated to achieving the Buddhahood in the future.  The Bodhisatta stands for the Mahapursas or the Great man, Mahasatta or the Great Being and  Buddhankura or the Buddha’s successor

                         The Bodhisattas both in the Theravada and Mahayana has been categorized in the different ways as follows: - in Theravada Buddhism it is divided into three kinds of virtues; the Bodhisatta of faith, of wisdom and of effort. In Mahayana Buddhism it is divided into two kinds; the Uttara Bodhisatta or superior Bodhisatta and Manusaya Bodhisatta or incarnated Bodhisatta. To the One who decides to follow the Bodhisatta’s path, he can take the holy order as a monk or as a householder. The practice of the perfections or Paramis is the most important path to attain the state of sublime. However, the Paramis or perfections in Theravada and Mahayana Buddhism have some different aspects.

                         The development of Bodhisatta has involved in many aspects and these were parts of the development of Buddhism such as the history of Bodhisattas in previous, present and future. Each of Bodhisatta has his own history that can refer to the Tipitaka and in Suttanta described the previous Bodhisattas who had already been the Buddha and the upcoming Buddha.

Besides, the development of ideology of Bodhisatta has involved in many aspects. The first ideology of Bodhisatta is to attain the Buddhahood in order to teach all human beings to get rid of the round of existence or samsara. 

       The study of Bodhisatta’ roles which influence on the Buddhists in the Mekong Sub-Region especially in both Thailand and Lao were  also done as the countries have the majority of Buddhist populations. From the proved evidences, the Bodhisatta has a long influence and played his roles to the Buddhists in this region. Since the first time of Buddhism establishment in this region, all kinds of  the Bodhisattas have become the important part of Buddhism. The ways of believes, the ways of tradition, literatures and the Buddhist art lie Buddhism.