Training for overseas Chinese language (CL) teachers is facing new challenges. In order to improve the effectiveness of training and facilitate teachers' professional development, it is important to investigate the current situation and understand the problems encountered in the training of CL teachers. This paper analyzes the insufficiency in CL teacher training in Southeast Asian in terms of training design, content and methods of training based on semi-structural case studies of eight young and mid-aged CL teachers from Singapore, Thailand, Indonesia and Myanmar. It proceeds to summarize the features of constructivist approach of teacher training and discusses its implications for CL teacher training in Southeast Asia. The findings will help teacher trainers to gain an in-depth understanding of the current situation and training needs of front-line CL teachers, advance the educational reform, and facilitate CL teachers' professional development.