I think the person who wrote that sentence is simply lazy. They did not mean "thou" in the old-fashioned sense for "you", but as an abbreviation for "though" or "although". Maybe this is fine in real shorthand, but otherwise it is not.
Also, "simplified" and "chinese" both require capital letters, as does "i" and, in theory, "traditional" too:
Although Singapore uses Simplified Chinese, I prefer Traditional.
(or)
Although Singaporeans use Simplified Chinese, I prefer Traditional.