I know many Korean speakers use "ㅋㅋㅋㅋㅋ" to express laughter. The "ㅋ" symbol has a sort of "kih" or "kuh" sound, so it's meant to represent a snickering "KihKihKihKihKih!"
In my experience, Brazilians do something similar, typing "kkkkkkk" (or sometimes "rsrsrsrsr," I suppose because riso=laughter in Portuguese).