Sukhumvit Road, or Thailand Route 3, is a major road in Thailand, and a major surface road of Bangkok and other cities. Sukhumvit Road is named after the fifth chief of the Department of Highways, Phra Bisal Sukhumvit. It is one of the four major highways of Thailand, along with Phahonyothin Road, Mittraphap Road and Phetkasem Road.
Sukhumvit Road begins in Bangkok, as a continuation of Rama I Road and Phloen Chit roads which span Pathum Wan district. Starting from where the boundaries of the districts of Khlong Toei, Pathum Wan and Watthana meet, it runs the entire length of the border between Khlong Toei and Watthana, then passes through Phra Khanong and Bang Na districts. It then crosses the border between Bangkok and Samut Prakan Province and subsequently continues east through Chachoengsao Province, south through Chonburi Province skirting the Khao Khiao Massif, east through Rayong Province, south-east through Chanthaburi Province, and ends at Ban Hat Lek village in Trat Province. In Chonburi Province it passes through the towns of Chonburi, Laem Chabang, Bang Lamung township, Si Racha, and Pattaya.

Source: https://en.wikipedia.org/wiki/Sukhumvit_Road