According to my version of the zip man-page, you need to use colons to separate the suffixes:
-n suffixes
--suffixes suffixes
Do not attempt to compress files named with the given suffixes. Such files are simply stored (0% compres-
sion) in the output zip file, so that zip doesn’t waste its time trying to compress them. The suffixes
are separated by either colons or semicolons. For example:
zip -rn .Z:.zip:.tiff:.gif:.snd foo foo
So you'd end up with:
zip -n .mp3:.wav:.3ga main_expansion thaisounds