This research article aimed to develop an online relationship marketing in mobile banking services that can fit in Thailand. The researcher employed quantitative research. The sample was 433 mobile banking users in Thailand. Data was collected through an online survey. The analysis of the overall harmony index of the model according to Thai people. After the researcher adjusted the model, it was found that the model was consistent with the empirical data. The coefficient of harmony of the 6 indices that passed the accepted criterion was ?2 = 149.313, ?2/d.f. = 1.990, RMSEA = 0.048, CFI = 0.978, TLI = 0.970, and SRMR = 0.036. The research found that online relationship marketing has a statistically significant direct effect on relationship quality, customer engagement, and loyalty. Relationship quality has a statistically significant direct effect on customer engagement and loyalty. This research article can be utilized by mobile banking service providers, agencies that make policies, and related departments and service businesses to ensure they develop and improve their service systems.