SUMMARY
One of the teaching materials for Indonesian language training is writing official letters. The purpose of this study is to develop a module that is used for Indonesian language training activities. This research method follows the stages of Borg and Gall development research. The research stages include preliminary research, collecting data for compiling modules, designing products, validating the product, design revisions, product trials, and product revisions. At the validation stage, the module was assessed for its feasibility as teaching material by three experts, namely material experts, media experts, and practitioners. After the module is validated, a trial of using the module as teaching material is carried out. Respondents who took part in the counseling were selected using a simple random sampling method. Based on the research, the results of the feasibility assessment were obtained by validators, trial participants and Indonesian language instructors. The results of the assessment show that the value of the feasibility of the module based on aspects of module content, language, presentation of material and graphics is between 89-95% with very worthy criteria. So it can be concluded that after going through the assessment and trial stages, the official letter writing module is suitable for use as teaching material in Indonesian language extension activities.