Phetchaburi is about 120km southwest of Bangkok, an easy two to two-and-a-half hour trip by road.
By bus: Regular services leave from Bangkok's Southern Bus Terminal (Sai Tai Mai) in Thonburi. The ride takes around two hours.
By car: Take Highway 35 (Thonburi-Pak Tho) through Samut Sakhon and Samut Songkhram, then Highway 4 south to Phetchaburi. The total distance is about 123km. You can also drive via Nakhon Pathom and Ratchaburi.
By train: Phetchaburi is on the southern railway line from Bangkok's Hua Lamphong station. Trains are slower than the bus but the route is scenic.