Whilst down in Southern Thailand, I was in a Tourist Office, and got a copy of Driving In Thailand: Southern Route.
The book measures 13cm x 20cm. It covers 15 southern towns, each with a detailed city and tourist map.
It has been very well put together, and I presume you should be able to obtain copies of Northern Thailand.
The book is a handy size as it easily fits in your bike jacket pocket.
