New Phetchburi Road is typical of many Bangkok streets in that it's romanisation from Thai is incredibly inconsistent. A street map of Bangkok may well spell the same road as New Petburi, New Phetchaburi, New Petchaburi or a few other similar spellings. Another example is Ratchadamri road - or should that be Rajadamri They are all one and the same thing, which can make things a little tricky when trying to find it on a map.
