This book is an easy guide to Bangkok's Songthaews in Thailand.
Songthaews are normally a fixed route mode of transport like the Buses. They travel on their daily routes and pick passengers up along the way. They are very cheap usually costing between 10 20 baht. But you will also get Songthaews that drive around looking for passengers like the red Songthaews in Chiang Mai. They operate like Tuk-Tuks and have no fixed prices. So, be very wary about being overcharged. Remember they have no seat belts and the rear of these vehicles is always open, so be safe at all times.
Also, a guide on how to purchase a Thai sim card for your smartphone (plus prices) so you can use roaming data for map apps, etc.