The Rae Sremmurd rapper is calling for all rap artists to stop touring in Sweden, and it sounds like the boycott could be indefinite ... because Jxmmi says no one should perform there until A$AP is released from jail and gives his blessing.

Slim has performed in Sweden in the past, but he says that's all over now ... he promises he won't return to the European nation until they change their laws and right their wrongs with A$AP.

As for the dangers posed by touring overseas ... Slim says it's real tricky, claiming he was almost detained once for smoking weed at a festival. His story sounds a little like the one Quavo shared with us last week, when he told our photog he was almost arrested in Sweden.

As we first reported ... A$AP's mom thinks Sweden is trying to make an example of her son -- who is has been in jail for weeks without being charged with a crime -- and she says there's a good chance race is factor.