On January 7, 2023, videos of audience members booing the Thai royal anthem—played with an on-screen request to stand silently in respect to the King—at the opening of a Blackpink concert in Bangkok went viral online. This incident marked the first widely recognized case of a collective vocal reaction to the anthem in Thailand. If participation in the ritualization of the national anthem materializes a unisonous sense of belonging to an imagined community (Anderson 1983), what identities were expressed, and through what forms of belonging, when collective booing clashed with conventional silence? Following Abe’s (2018) framing of human sonic expression as socially embedded across sedimented histories, I analyze online reactions to the incident alongside archival research on the anthem’s history. Rather than a planned protest, the boos signaled audiences’ discomfort with the anthem as a symbol of Thainess that did not resonate within Thai Blackpink fandom, particularly as fans expressed their pride in welcoming the group’s Thai member, Lisa, home. As noted by K-pop scholarship (Siriyuvasak and Shin 2007; Wee 2021; Lee and Kao 2021), the genre generates imagined communities through shared consumer culture, complicating historically constituted national identities and boundaries. Through booing, audiences contested the royal anthem, which has long been an emblem of Thai royal nationalism since the formation of the Thai nation-state in the late nineteenth century. This vocalization reverberated in a space celebrating a stylish, glossy Thainess shaped by inter-Asian pop cultural circulation.