The calculated distance (air line) between Nakhon Si Thammarat and Ko Samui is approximately 76 miles respectively 123 kilometers.
By car or train, the actual journey to Ko Samui is certainly longer, as only the direct route (as the crow flies) between Nakhon Si Thammarat and Ko Samui has been calculated here.
Air line (approximately)
123 kilometers
66 nautical miles