Hugo Chavez was a populist at home and a third-worldist abroad.
The two go together. Third-worldism is populism at the international level.
Populist rhetoric is about the people versus the elites. Third-worldist rhetoric is about the third world versus the first.
Populism has left- and right-wing variants. So does third-worldism. Chavez and Ahmedinejad came together a third-worldists. Chavez was a leftist, Ahmedinejad a religious fundamentalist.
Populism is vague about actual policy. So is third-worldism.
Populist talk is entirely compatible with authoritarian practice. Third-worldism is not only compatible, but often a cover for, authoritarianism.