Nakhon Si Thammarat is a city (thesaban nakhon) in southern Thailand, capital of the Nakhon Si Thammarat Province and the Nakhon Si Thammarat District. It is about 610 km south of Bangkok, on the east coast of the Malay Peninsula. The city was the administrative center of southern Thailand during most of its history. Originally a coastal city, silting moved the coastline away from the city. The city has a much larger north to south extension than west to east, which dates back to its original location on a flood-save dune. The modern city centre on the train station is north of Old Town. As of 2019, the city had a population of 102,152.