Thailand is the first line of the railway line in Bangkok - Nakhon Ratchasima . Notification of Siam railroad . Bangkok The city of Nakhon Ratchasima , dated 22 March 2434 , but it appears that not long after construction . The British built a railway concessionaire can not be completed as promised. Royal Railway Department had already terminated the construction itself and enable the early Bangkok - Ayutthaya ( 71 km) on 26 March 2440 .