Is there a way to input a specific language with keyboard that is not supported by the android I'm using Mi 4i and I wanted to input Thai by using a bluetooth keyboard logitech K480.

I couldn't find out how to input by Thai and asked support center of Xiaomi.
The clerk said that the input Thai with bluetooth keyboard is not supported by Mi 4i.

Is there a way to "activate" or make it possible to input Thai with keyboard?
Try External Keyboard Helper Demo from Apedroid (full version here). It says in the description it supports Thai keyboards.

Also, check out this thread