Mukim Kuala Belait is a mukim in Belait District, Brunei. The population was 31,308 in 2016. The mukim encompasses Kuala Belait, the admiā¦Mukim Kuala Belait is a mukim in Belait District, Brunei. The population was 31,308 in 2016. The mukim encompasses Kuala Belait, the administrative town of the district. The mukim is the located in the westernmost part of the district as well as the country. It borders the South China Sea to the north, Mukim Seria to the east, Mukim Kuala Balai to the south-east and the Malaysian state of Sarawak to the south and west.