Wellness tourism is a rapidly growing field within medical and public health sciences. This study examines wellness tourism in Thailand by investigating the effects of service marketing factors (7P) and tourism activity factors on tourist satisfaction and behavioral intentions, with a focus on gender differences. Data were collected from 1,200 wellness tourists and analyzed using structural equation modeling (SEM) and multiple group analysis (MGA). The study integrates the 7P framework, Activity-Based Tourism Models, and behavioral intentions within a single model. The findings reveal gender-specific differences. Male tourists place the greatest emphasis on service process, whereas female tourists consider physical evidence the most important factor. Activity Effect and Activity Experience significantly influence male tourists’ satisfaction, while Activity Cost does not. In contrast, all three activity dimensions significantly and positively affect female tourists’ satisfaction. Satisfaction also significantly predicts behavioral intentions to use wellness services for both genders. Based on these findings, the study proposes strategic policy recommendations tailored to gender-specific preferences and expectations. The results offer valuable insights for policymakers and tourism and public health stakeholders, contributing to the competitiveness and sustainable development of Thailand’s wellness tourism industry.