The first section starts at Amphoe Mueang Nakhon Si Thammarat.
It goes south-westward and ends at Amphoe Kantang Route 403 is main road that connect Nakhon Si Thammarat and Trang.
The 1st section starts at Hua Thanon junction in Amphoe Mueang Nakhon Si Thammarat.
It turns left to the south, pass Route 41 and goes into Trang Province.
It finally ends by joining with Route 4 near Amphoe Huai Yot.