Many employers in Thailand, while depending on migrant workers to grow their businesses, may still be reluctant to invest in skills training for migrant workers. Although various training benefits have been observed for migrant workers, the business case for training migrant workers from an employer perspective has not yet been clearly demonstrated. Against this background, the objective of this report is (1) to outline benefits of training migrant workers, and evidence showing these benefits, based on a review of the literature on employers’ returns on investment in training; (2) to show how training costs and benefits can be measured, to support investment decision; as well as (3) to showcase the application of the return on training investment (ROTI) methodology in two case studies featuring companies in Thailand. This methodology serves as a guide for employers to make informed investments in skills development programmes for migrant workers.