Relationship marketing (RM) is widely acknowledged as a useful tool in gaining customer loyalty in various sectors. However, to date, there had been no research on how RM impacts customer loyalty in the securities brokerage firm industry in The Stock Exchange of Thailand. This study employs an inductive research approach to explore RM in securities brokerage firms in Thailand’s financial services sector and gain an understanding of customers’ and other stakeholders’ views of RM activities and loyalty to brokerages in an emerging market. Multiple data collection methods were employed, including semi-structured interviews as the main collection method and participant observations in a supporting role. Qualitative content analysis and coding techniques were used for analysing the data. This pioneering 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, for example, RM’s positive impact on individual short-term investors’ loyalty, not to brokerages, but to particular staff.