In 1894, the Danish engineer Aage Westenholz (1859–1935), uncle of the writer Karen Blixen, was given the concession to build a route from BangkoktoPhetchaburi. The project failed due to the difficulty of raising sufficient capital. As a result, the Thai state decided in 1898 to build the main rail lines itself and bought back the concession. Other concession requests made by railroad entrepreneurs in the Thai part of the Malay Peninsula were all rejected.
After the Thai state had bought back the West timber concession, the Royal Railway Department (RRD) in the Ministry of Public Works planned a route, under Karl Bethge from the Krupp Company, to Phetchaburi. The construction work began in April 1900.
Because of the length of the route, construction occurred simultaneously in three sections:
from Phetchaburi to the south
from the port Songkhla on the east coast
from Kantang port on the west coast of the Malay Peninsula.
In contrast to the rest of the Thai railway network, which was built in standard gauge, the Royal State Railways of Siam chose the metre gauge to allow for a seamless connection to the metre gauge railways of Burma and Malaya.
The Southern Railway was isolated from the rest of the network, starting from a terminus in Thonburi, on the west side of the Chao Phraya river as there was no bridge across the river. Thonburi station was accessible by ferry from the east side of the Chao Phraya river. The building was designed in the style of brick expressionism by the German architect Karl Döhring, engineer with the Royal State Railways of Siam. It is now a Medical Museum.
On 1 April 1903, traffic on the first completed section between Thonburi and Phetchaburi was operated with makeshift carriages, as delivery of a significant portion of the rail vehicles was delayed. When these had arrived, the official opening was held on 19 June 1903 by King Chulalongkorn (Rama V.)
More sections followed successively from 1911. The opening dates are as follows:
1911: Phetchaburi–Hua Hin in two sections,
1913: Kantang–Huai Yot
1 January 1914: Kantang–Thung Song Junction
1 January 1914: Songkhla–Phatthalung
1 January 1914: Hua Hin–Wang Phong
1 October 1914: The sections driven by Kantang and Songkhla were merged.
1 October 1916: The southern and the northern parts of the line were merged at Chumphon and continuous operation could occur.
On 1 July 1918, trains were able to operate from Thon Buri Railway station to Malaysia via Padang Besar. The initial service was two trains per week and the journey time took 60 hours.
An official opening ceremony did not take place because of World War One. Long-distance trips were interrupted for overnight stays with the Royal State Railways of Siam providing hotels at major train stations. In 1922, night traffic and sleeping cars were introduced and the travel time from Bangkok to Penang reduced to just over 30 hours.
The Railway was forced to relinquish the metre gauge line, already built under its direction from Bangkok Thonburi to Phetchaburi to the Southern State Railway. This was not only technically reasonable, because it provided a uniform administration for each of the two gauges operated by the state, but also a political balancing act of the Thailand, which until 1917 was neutral in the First World War. The northern RRD worked under the German director Karl Bethgen, the southern under the British Henry Gittens, whose countries of origin were now enemies of the war.
After Thailand's entry into the war on the British and French sides on July 22, 1917, the connection of the Malay and the Thai railway network received high priority. Initially, it was planned to establish the connection via the east coast of Malaysia following route. The construction progress of the track in Malaysia was slow. So the authorities decided to establish a connection with the Malay West Railway. This was put into operation in 1918. The route over the eastern border crossing Sungai Kolok could only go into operation on 1 November 1921.
Construction started in December 1922 of the Rama VI Bridge (Thai: สะพานพระราม 6) over the Chao Phraya River during the reign of Rama VI. Opened on 1 January 1927 it linked the Northern and Eastern rail lines with the Southern railway and allowed Southern Railway trains to operate into Bangkok Hua Lamphong railway station.
In 2003, the terminus of the line westward to the previous station Bangkok Noi, was relocated and the vacated railway area was utilised for the extension of Siriraj Hospital. The Bangkok Noi station reverted to the name Thon Buri railway station.
The Southern Line consists of the Su-ngai Kolok Main Line which stretches from BangkokHua LamphongtoSu-ngai Kolok District, Narathiwat Province, in the far south of Thailand, 1,140 kilometres from Bangkok. There are seven branch lines off this main line:
Hat Chao Samran Railway (1921–23): South of Phetchaburi consisted of a 12 km long "siding" on the beach of Hat Chao Samran, which served only that 1921-1923 King Vajiravudh (Rama VI) and his court could travel by special train directly to the local summer palace. The branch station for this connection was called Phra Ram Ratchaniwet and was abandoned as well as the track to Hat Chao Samran when the king did not go there in summer.
Songkhla Branch Line (1914–1978): The section south of Songkhla, is 29 km long and was opened on 1 January 1914. The branch station was initially U-Taphao Junction (925.80 km from Bangkok). The location of the branch station was a poor choice as it was located in the flood area of Khlong U-Taphao. TAs a result the branch was relocated in 1922 to the newly built Hat Yai Junction (km 928.58). The Songkhla branch line was shut down on July 1, 1978.
The Southern Line has been the target of terrorist attacks of the South Thailand Insurgency especially between the Hat Yai-Sungai Kolok section. All stations and halts between Hat Yai Junction and Sungai Kolok have been fenced off and gates are opened and closed only during operating hours. Trains operate only during the day between 06:00 and 18:00.
