The calculated distance (air line) between Chanthaburi and Phra Nakhon Si Ayutthaya is approximately 158 miles respectively 255 kilometers.
By car or train, the actual journey to Phra Nakhon Si Ayutthaya is certainly longer, as only the direct route (as the crow flies) between Chanthaburi and Phra Nakhon Si Ayutthaya has been calculated here.
Air line (approximately)
255 kilometers
137 nautical miles