This research proposes a dispatch strategy to Mae Hong Son (MHS) power system which is classified in 2 modes of operation: the normal mode and islanding mode. In this research, we design dispatch strategy of energy management system (EMS) using various renewable sources within MHS. In normal mode operation, we model the power system components in linear model and formulate EMS as linear program to solve for the optimal dispatch. Multi-objective function approach aims to minimize Total Operational Cost (TOC) and Total CO2 Emission (TCOE). In addition, we add Battery Energy Storage (BES) to the power generation and compare the results of operation to that of existing system as of 2014. In islanding mode, we go through various possibilities such as fault at day/night time, with/without BES. We formulate the dispatch strategy after fault subjected to constraints on hybrid power generation, battery state of charge, and power balance principle along with the power system condition. The results show the dispatch profiles of MHS power system based on the optimal operation.