Nakhon is the regional capital of the Nakhon Si Thammarat province, and is one of Thailand’s oldest cities, dating from at least the 7th century and certainly prominent as a large city during the times of Sukhothai and Ayutthaya.
It is located on the east side of the Thai peninsula, a couple of hours drive south of Surat Thani, which most folks will pass through on their way to somewhere like Koh Samui.