Low gear either 2 or even 1 can be used to go up-hill, it keeps the speed down but the rev's higher to help the engine and prevent stalling, just as they can be used as engine breaking going down hill.
I don't have any issue with the road/street signs.
But Thai only script on buses/vans etc is confusing... road side bus stops have little or no information and where the hell are they going and is this the bus I want?