The purpose of this study was to explore how a regional brand can be co-created among different cities by employing the concept of place branding and brand culture. The Andaman Tourism Cluster of Thailand (ATC) generates the most tourism revenue in Thailand. Developing a regional brand identity can strengthen the competitive advantage of the ATC. Data were collected using multi-method research through questionnaires, projective techniques, and focus group interviews. Quantitative data were analyzed using descriptive and inferential statistics, while qualitative data were analyzed using thematic analysis. This study also shows that multi-method research contributes to brand management by facilitating collaboration, participation, and brand congruence among stakeholders. Quantitative and qualitative data were synthesized in order to develop the brand identity of the ATC. Focus group interviews were also employed to co-create the regional brand identity as ‘Irresistible Andaman’, of which sustainable tourism management is a fundamental aspect. This study demonstrates how multiple sub-brands with different stakeholders can be integrated into a single regional brand. Moreover, stakeholders should focus on internal branding by communicating with all stakeholders to co-create brand congruence.