Monkeys have been used as a racial slur against Black people and it has the implication/suggestion that someone is only partially human and more beastly or primitive. In addition, Masego adds that this person is 'slangin' thangs.' Natives have constantly been considered 'tribal' or 'primitive' because we like to maintain our old stories and traditions. I'm not sure if he means this person is hustling or if this person he is referring to is selling drugs. Either way, it's pretty unclear what he means in this line.