Thai keyboard support

[daoshengmu]

Is your feature request related to a problem? Please describe.
Adding Thai keyboard support maybe its display language as well.
https://trello.com/c/DN3JoStB/538-uis-92-thai-keyboard

Describe the solution you'd like
I already done UI layout work in local, but I aware iOS and Android are doing differently when dealing vowel symbols. Android generally do not show vowels when it can't be combined with a character. iOS allows it. We also need to figure out how to combine multiple vowels with a character. Android allow add multiple vowels not iOS can't. We are seeking for native speakers' opinions.

Describe alternatives you've considered

Additional context