Probably lower for simplified Chinese and katakana/hiragana Japanese characters.
I'd say that at 2x2, "Two Slice" is definitely not readable.
8x8 for Chinese is difficult, but I think it’s a bit less guesswork than 2px high for English. I wonder what simplified Chinese would look like 6px tall.
5x7(7x5) is smallest I could find for Japanese, it probably won't work for actual Chinese language though