I recently lost my mobile phone here in Thailand. Which was unfortunate.
However, when I replaced it (with the exact same model) it had a Thai language on the internal system! Now every time I use my phone, it is in Thai! This is something that I’m actually really excited about!
A couple of years ago when I had a Blackberry Curve 8520, I famously changed the operating system of the phone and also case-modded it, so the phone physically had a Thai keyboard.
My current phone is an Android phone (Samsung Galaxy Ace) and there’s no need to do any crazy physical case modding to change the input language! However, changing the actual system language is a very difficult thing to do.
It also adds another layer of immersion and helps me learn Thai. When I use it as an alarm clock, the first thing I’m greeted with everyday is prompt in Thai! That really helps to wake me up!