I recomment you install "google search" on your car. Then you can search the location with that and then transfer the location to the Onboard Navigation.
I also had my problems somtimes to find the desired location, especially when you only have a name of a spot and not the exact location with street name.
With the google search app (you need internet, this I do with WiFi sharing from my phone) so I can use the google engine to find the place I want.. and then the app give the coordinates to the Navigation onboard system. This works always.
Bye the Way, even when searching with thai letters I not always can find the place, if I only have the name of the spot. So I don't think it's a problem of poor translation as more of the onboard navi not have that many places availabe.