Danklang U.Leelasantitham A.Mahidol University2026-03-192026-03-192026-03-01Sustainability Switzerland Vol.18 No.5 (2026)https://repository.li.mahidol.ac.th/handle/123456789/115778This study examined the psychology-driven decision-making dynamics of Millennial solo travellers in Asia, with a comparative focus on Thai and other Asian tourists. While the Theory of Planned Behaviour (TPB) is widely applied in tourism research, prior studies may not fully address the attitude-mediated construct–intention gap, stage-based intention–behaviour variation, and post-intention outcomes. To extend this perspective, the study proposes the I-SMART Cognitive TPB Model, integrating temporal bias, loss aversion, narrative-driven information, Social Exchange Theory, the four-stage tourism life cycle, and post-intention marketing behaviours. Survey data from 800 respondents (400 Thai, 400 Asian) were analysed using structural equation modelling. The findings indicate that narrative information may play a stronger role in shaping attitudes among Asian travellers, whereas Thai travellers appear more influenced by time-based motivation. Pre-trip factors emerged as key contributors to intention formation in both groups, while post-intention patterns diverged: intention linked more strongly to satisfaction among Asian travellers and to revisit tendencies among Thai travellers. Theoretically, the study offers an integrated cognitive–behavioural model that complements TPB by incorporating bias-driven and stage-based mechanisms. Practically, the findings provide guidance for designing digital infrastructure, time-sensitive policies, and storytelling-driven marketing strategies tailored to Millennial solo travellers.EnergyEnvironmental ScienceComputer ScienceSocial SciencesArticleSCOPUS10.3390/su180522652-s2.0-10503270029720711050