I used to use my GPS phone with Google Maps until I bought a local satnav. Used that, though it often tried to make me turn where there was no turning. I think it because they are programmed with mao data that is not updated like it is in the west. Roads are forever changing here. Anyway, I used it everytime I went anywhere until I broke it last year. Now I don't need it - it held me back from learning the way around. Sure I got lost a few times, but paper maps in the car/bike help then - so does asking (that is always fun - everyone is so helpful here they will point out where to goi even if they have no idea themselves!). The none I had allowed for both Thai and English input and still navigated in English. It also had a large memory of local places and shops.
I have to concur with Mark though as to spelling. It is really inconsistant here - Google Mapos gives different spelklings, as do paper maps, compared to that which the device took - and I mean in both Thai and English. Often Thai places have prefixes etc, that are in the machijne, but not on maps, addresses etc. Also some roads close at certain times and can be a real pain when the satnav is determined to take you down a closed road.
The other issue I had was the way roads change here. A perfectly straight road may changenames a dozen times in a Km - and I don't kow if it was my machine or what, but I forever got turn left into blblblblblblr Road etc, when it was actually straight on - I got used to looking at the screen to confirm each spoken command in the end - never a great policy when in town.