The calculated distance (air line) between Teknāf and Uttar Char Fasson is approximately 139 miles respectively 224 kilometers.
By car or train, the actual journey to Uttar Char Fasson is certainly longer, as only the direct route (as the crow flies) between Teknāf and Uttar Char Fasson has been calculated here.
Air line (approximately)
224 kilometers
121 nautical miles