Ritual multilingualism in Islamic communities is often viewed as syncretic, hybrid, or acculturative. Such forms rarely reflect an indexical hierarchy of language use. This study examines how linguistic hierarchy is organized within the Ulu Kapuas Malay or Melayu Ulu Kapuas (MUK) incantations of West Kalimantan, Indonesia. The study draws on 72 incantation texts categorized by the community as tawar, cuca, ilmu, and jayau, supported by in-depth interviews with custodians of the MUK cultural traditions, as well as contextual field documentation. The data were coded according to language choice (MUK, Arabic, and Indonesian) and structural position within the ritual text (opening, core, and closing), and then analyzed qualitatively to identify recurrent functional patterns in ritual performance. The interpretation focuses on how these patterned distributions index religious authority, cultural legitimacy, and communicative mediation. The findings show that ritual multilingualism in this corpus is not an eclectic mixture but a structured semiotic hierarchy. MUK consistently serves as the performative core of ritual action and grounds it in emic cosmology. Arabic appears primarily in the opening and closing formulas of the incantations, serving to frame the rituals and sacralizing and legitimizing in ritual. Meanwhile, Indonesian functions more peripherally as a narrative and mediating code, occasionally supporting communicative clarity without displacing the ritual role of the MUK. By demonstrating that local efficacy and Islamic legitimacy are jointly produced through distinct linguistic roles, this study enhances the socio-linguistic understanding of the relationship between language and religion from the perspective of local communities.