The Thai highway network follows the left-hand traffic rule of the road. The network is the twin responsibility of the Department of Highways, and the Department of Rural Roads, under the oversight of the Transportation ministry of Thailand. Public highways are also called public roads, especially when part of urban streets. The network spans over 70,000 kilometers across all regions of Thailand. Most are single carriageways. Dual carriageways have frequent u-turn lanes and intersections slowing down traffic. Coupled with the increase in the number of vehicles and the demand for a limited-access motorway, the Thai Government issued a Cabinet resolution in 1997 detailing the motorway construction master plan. Some upgraded sections of highway are being turned into a "motorway", while other motorways are not being built from highway sections.

Phahonyothin Road or Highway 1 is a main road in Bangkok and one of the four primary highways in Thailand, which include Mittraphap Road, Sukhumvit Road, and Phet Kasem Road. It begins at Victory Monument in Bangkok and runs north to the Burmese border, with a total length of 1,005 km (624 mi).