I just installed NAVV Globetrotter for Iphone, a free app that comes with a free downloaded map of your choice and 30-days free voice navigation.
As far as I understand you can get 1 map for free, others have to be bought but I am not sure of that yet.
So I downloaded Thailand map and it seems to work. And I checked some locations/streets I know and it is all on the map. Even the King Hotel in Loei is in the list of POI.
Although I must say that scrolling & zooming with the map does not work that smoothly but otherwise I think I like it.