When spoken, this sentence could also be understood as "the child, too", if the stress is on "myös". But it wouldn't be entirely correct.
The correct ways to express that would be either "Myös lapsi puhuu koreaa" or "Lapsikin puhuu koreaa". We love our endings! :-)
Lapsikin could actually even be understood as "everyone, even children", for example when saying "Lapsikin ymmärtää,", even a child would understand (something).