Phahonyothin Road or Highway 1 is a main road in Bangkok and one of the four primary highways in Thailand, which include Mittraphap Road (Highway 2), Sukhumvit Road (Highway 3), and Phet Kasem Road (Highway 4). It begins at Victory Monument in Bangkok and runs north to the Burmese border, with a total length of 1,005 km.

History

Phahonyothin Road was originally called "Prachathipat Road" (, Thanon Prachathipat, literally "Democrat Road"), and reached just 22 km to Don Mueang. In 1938, Field Marshal Plaek Phibunsongkhram had the road extended from Don Mueang, through Bang Pa-In, Ayutthaya, Saraburi, Lopburi, and Singburi, making it 162 km long. The newly lengthened road was renamed Phahonyothin Road, in honor of General Phraya Phahol Pholphayuhasena (formerly Phot Phahonyothin), the second Prime Minister of Thailand and one of the heads of the 1932 revolution.

Route

In Bangkok, Phahonyothin Road originates at the northeast corner of Victory Monument on the periphery of Ratchathewi and Phaya Thai districts, then crosses Chatuchak, Bang Khen, Don Mueang, and Sai Mai districts before continuing into Pathum Thani Province, and on through Ayutthaya, Saraburi, Lopburi, Nakhon Sawan, Chainat, again through Nakhon Sawan, Kamphaeng Phet, Tak, Lampang, Phayao and finally Chiang Rai, ending in Mae Sai district, where it connects to Tachileik in Myanmar. Phaholyothin Road in Bangkok is also a demarcation line between districts or sub-districts in several phases as follows: