Have recently noticed a huge uptick in the amount of non-English (especially Chinese) spam, which slips through the SpamAssasin nets much more readily than English spam (at least it does in most Western SA setups; not sure how different things are for, say, Chinese hosts).
Turns out you can tell SpamAssassin to give higher ratings to messages written in languages other than those you’ve explicitly sanctioned. Higher ratings mean more likelihood of messages getting tossed to /dev/null or saved in a junk box. In your local.cf or user_prefs, just add:
ok_languages en de la th sv
(e.g.) to accept messages in English, German, Latin, Thai, and Swedish. Full list of language codes here. Works a treat.