Samut Prakan is at the mouth of the Chao Phraya River on the Gulf of Thailand. Thus the province is also sometimes called Pak Nam (ปากน้ำ), the Thai word for the mouth of a river. The part of the province on the western side of the river consists mostly of rice paddies and prawn farms as well as mangrove forests, while the eastern part is the urban centre, including industrial factories. It is part of the Bangkok metropolis. The urbanization on both sides of the provincial boundary is identical. The province has a coastline of approximately 47.2 kilometres.