Lads
you cn sellect in garmin to avoid TOLL roads and as per Rays Zumo 450 and mine 550, that option works,,i tested that, so in that way it gives you route,,what ever it thinks is the either fastest or shortes,,, how ever in ZUMo it self one can do 'Own' routes in the zumo display, this need's a little bit practice when use it but ones you get top of it, it's fantastic in Garmin it called 'Routes' button.
Also as mentioned by pseacraft, mapsourse is good, but again with new thailand map that can be done and then import that to Garmin, it will then automatically insert that in to NEW routes, again that need a little 'Play' around normally.