click Change Keyboards

Now, click Change Keyboards to add another keyboard language or change your default one.

Our default input language is US English, and our default keyboard is the US keyboard layout.  Click Add to insert another input language while still leaving your default input language installed.

Here we selected the standard Thai keyboard language (Thai Kedmanee), but you can select any language you want.  Windows offers almost any language you can imagine, so just look for the language you want, select it, and click Ok.