Growing environmental concerns and seismic safety requirements have intensified the need for innovative building materials in the construction industry. This challenge is particularly acute in seismically active regions like Indonesia, where the convergence of the Indo-Australian, Pacific, and Eurasian tectonic plates creates unique structural demands for buildings and infrastructure. This study investigates the development of lightweight foamed concrete incorporating oil palm kernel shell (OPKS) as a sustainable aggregate for earthquake-resistant construction applications. The research comprehensively examines the effects of surface modification using silane-siloxane nanocoating and optimizes cement-to-OPKS ratios (2.5:1, 2.7:1, and 3.3:1) across different target specific gravities (1.0, 1.2, and 1.4). The experimental program involved preparing OPKS specimens with both uncoated and coated treatments, followed by characterization of their physical and mechanical properties. Density stability, compressive strength, and tensile strength development were monitored over a 28-day curing period. Microscopic analysis revealed significant morphological modifications resulting from surface treatment, contributing to enhanced aggregate-matrix bonding. Results demonstrate that higher s.g. mixtures (1.4) achieved superior stability and strength performance, reaching 8 MPa for specimens with CT aggregates. Surface treatment significantly enhanced concrete workability and reduced moisture absorption, particularly evident in specimens with higher cement content. The study establishes that OPKS-based lightweight foamed concrete represents a viable solution for non-structural building elements in seismically active regions, particularly for applications requiring compressive strengths below 3 Mpa (residential wall applications). This research contributes to sustainable construction practices by effectively utilizing agricultural waste while meeting structural safety requirements for residential applications.