According to this Knowledge Base article on languages Thai is currently not supported as profile language: http://community.lithium.com/t5/Community-display/Languages-that-Lithium-supports/ta-p/6566
As Lithium is storing content in UTF8 format you can host content in Thai language in your community.
We do now support Thai on our community platform, as of Nov/Dec, but our social media monitoring product does not. The article Claudius mentioned has been updated.
Thanks for asking!