The calculated distance (air line) between Bangkok and Phra Nakhon Si Ayutthaya is approximately 42 miles respectively 67 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 Bangkok and Phra Nakhon Si Ayutthaya has been calculated here.
Air line (approximately)
67 kilometers
36 nautical miles