I think it would be better if you wrote: Cantonese is also widely spoken BY CHINESE PEOPLE in Southeast Asia such as in Vietnam and Malaysia...
I'm not sure in Malaysia, but in Vietnam, Vietnamese people we don't speak Cantonese. Only Chinese people, who emigrated from China ti Vietnam not for along time ago, and really small part of Vietnamese, who living next to them, speak this language.
By the way, in Vietnam the Cantonese be changed a little bit in tone, in accent too, to be able to use here.
