Continuing Professional Development (CPD) of teachers has been seen as one of a key element to improve teacher quality and the quality of education in many countries, as well as in Thailand. The current Thai education reforms have recognized the importance of CPD for teachers to maintain and update their knowledge and skills to be able to teach students effectively. They also recognized the need of effective leadership in schools to lead, manage, and support teachers in order to achieve such change. The purpose of this study is to support CPD experiences for teachers to enhance teaching practice and improve student achievement. It was undertaken using a combined methods investigations of both quantitative and qualitative data to understand the current situation of CPD experiences for teachers in Thailand, and extend the knowledge of effective CPD. The study covered respondents from a survey of teachers, and the interviews of headteachers and teachers from selected schools in Chiang Mai, which is located in the North of the country. It was concluded in the study that most respondents were appreciated opportunities for CPD and valued the benefits of CPD to teachers, students, and the schools as a whole. With the increased expectations for highly qualified teachers, all schools need to provide the necessary support for teachers through a range of CPD experiences to enable them to teach to high standards. CPD must be of the highest quality to be effective in order to enhance the teaching practice and student achievement. The study hope that the results and information provided here would be valuable for anyone who are interested in, as well as those who are responsible for an improvement and implementation of CPD.