The Association of Southeast Asian Nations (ASEAN) has long pursued the ASEAN Power Grid that could promote energy security while increasing the renewable energy deployment into the grids. To inform the implementation of the APG, ASEAN Interconnection Masterplan Studies (AIMS III) Phase 3 will be conducted to lay out the foundation for establishing a multilateral power trade in ASEAN. As part of the AIMS III Phase 3 studies, the main output of this Terms of Reference will be a report on the proposed harmonisation of grid codes and minimum operational technical standards for interconnections under ASEAN Power Grid. The implementation of this project will be done in close coordination with the ASEAN Power Grid Advancement Program (APG-AP) consortium members.