The convergence of social media with political communication and the emergence of celebrity politics have significantly altered the landscape of political participation, particularly among the younger generation. Yet, comprehensive research on online political fandom remains limited despite its critical intersection with politics and digital media. This study addresses this gap, focusing on the in-depth case study of the 2020-2021 Thai anti-government protest. It scrutinises how tech-savvy Thai youth, propelled by political fandom surrounding Thanathorn Juangroongruangkit, a Future Forward Party opposition leader, harnessed social media and pre-existing online networks to organise these anti-government protests. Despite lacking a formal hierarchy, their organisational prowess, especially in information dissemination, highlights the intricate interplay of political fandom, social media, and youth mobilisation. By employing a trace interview method and conducting semi-structured interviews, the study explores how political fans transitioned from online engagement to active protest participation. The evidence contributes to a nuanced understanding of how fandom culture shapes their political judgment and behaviour. Participants in this study are political fans who publicly engage with politics on social media and participate in large-scale protests offline. They were recruited through a two-step process: first, the Twitter API identified users with high engagement in political fandom and anti-government hashtags. Then, a snowball sampling method extended the participant pool based on referrals from initial interviewees. A thematic analysis was conducted on the interview transcripts. The initial findings indicate that the influence of charismatic political figures, the empowerment of the fan community, and the belief that online political expression is ineffective draw participants toward offline participation. The resemblance between the political fandom of Thanathorn Juangroongruangkit and the more mainstream popular fandoms highlights the importance of considering the role of popular culture influences in shaping people’s political behaviours, particularly in contemporary digital communication technologies. In conclusion, this study aims to uncover the intricate relationship between political fandoms, social media, and offline activism and to emphasise the pervasive influence of popular culture on political behaviours in the digital age.