This research provides new theoretical and practice knowledge and delivers a far more subtle and nuanced analysis of the dynamics at play between customer loyalty, various RM strategies and different customer types – compared to the current literature. The study found that securities brokerage firms in Thailand implemented RM practice but with differences in relationship marketing strategies, depending on the types of customers being targeted. The study identified the main factors impacting on customer loyalty to both local and international securities brokerage firms. Finally, the research confirmed that RM had a demonstrable impact in gaining customer loyalty to securities brokerage firms in The Stock Exchange of Thailand (SET), but with intriguing characteristics, e.g. RM’s positive impact on individual short-term investors’ loyalty, not to brokerages, but to particular staff