Samut Prakan is 29 kilometres away from Bangkok, down to the south where Chao Phraya River meet the Gulf of Thailand.
The province was established during the period of Ayutthaya and had an administrative centre at Prapadaeng. It was the Siam pier that was defended with forts, ditches around the town and town walls. In 1819, King Rama II decided to rebuild the new centre at Samut Prakan, after the previous King Taksin had neglect the city fortress. He has constructed new six forts on the sides of Chao Phraya River and set up Phra Samut Chedi, the pagoda, in the river on an island.
The coastline of Samut Prakan is approximately 47.2 kilometres long.