 It begins at Naowa Chamnian bridge in Bangkok Yai, Bangkok.It is named after Luang Phet Kasemwithisawasdi, the seventh director general of the Department of Highways.The provinces along the road are Samut Sakhon, Nakhon Pathom, Ratchaburi, Phetchaburi, Prachuap Khiri Khan, Chumphon, Ranong, Surat Thani, Phang Nga, Krabi, Nakhon Si Thammarat, Trang, Phatthalung and Songkhla.