Food waste has a high potential for greenhouse gas (GHG) emission, particularly methane, which has been causing climate change issues worldwide. This quantitative research is aimed to investigate the situations of food waste and assess its greenhouse gas emission potential in Thailand. Food waste management in eight municipalities was analysed across four regions countrywide. The findings showed that the COVID-19 pandemic led to a dramatic reduction in municipal food waste (MFW). This led to a total of around 26,657 tonnes/day in 2021, which was nearly 39% of the total MSW and the average MFW generation per capita was 0.4 kg/capita/day. Household food waste (HFW) represented a major component of MFW. In large urban municipalities and cities (notably tourist cities), significant food waste per capita exceeded the peri-urban municipalities (P < 0.05). Moreover, the treatment of MFW could result in significantly higher GHG emissions than from fossil fuel emissions created by the collection and transportation of MFW. This comparison between the four food waste management technologies that emits the most greenhouse gases showed that landfill had the most GHG emission potential, followed by incineration, composting, and anaerobic digestion, respectively. The research findings clearly illustrated that the municipalities at all levels needed to take the following actions: 1) conduct a survey and study the situations of food waste problems in local area, 2) formulate the policy for food waste management and treatment using the appropriate selection of technologies available with a minimum of impact on the environment and the Earth’s atmosphere, and 3) utilise the GHG emission potential for food waste disposal, such as energy recovery as well as possible trading-in for carbon credit.