Objective: To compile the Unweighted Green Banking Disclosure Index (UGBDI) for banks in Southeast Asia. The index is developed to provide a more suitable disclosure measurement for banks in the region, considering that existing green banking assessments are often based on standards from developed countries. Method: Using a literature review approach based on green banking regulations in Southeast Asian countries and previous studies. The index preparation was conducted through several stages, including identifying definitions and keywords, discerning and classifying similar items, synchronizing them with existing standards, and formulating new disclosure items. Results: Resulting in 32 green banking disclosure items for banks in Southeast Asia. These items were developed from regulations and prior studies, then synchronized with sustainable banking assessment standards. The resulting index can be used by banks, researchers, and regulators as a reference for evaluating and improving green banking disclosure practices. Novelty: Developing an original Green Banking Disclosure Index tailored to the Southeast Asian context by integrating regional green banking regulations and previous studies. The index contributes to SDG 13 (Climate Action) by enhancing climate-related disclosure practices and supporting the transition toward sustainable finance in the banking sector.