You have the gui language and the map language (General settings -> Preferred map language). The map language gives you the option to use local names or in your language or english (default fall-back language).
Of course the objects need to have english names, which is mostly only valid for big city names.
So even if you set the map language to english you will hardly find any more (I expect).
However: if you mean that you want the "scribbly" thai characters displayed in "latin" characters, you will be disappointed. That is not at all possible.
Harry