I'm pretty sure it happened many times? Not all cultures are rampaging hordes like the west Europeans, though even then given enough time and contact conflict becomes more likely to arise.

For essentially peaceful first contacts, the Chinese treasure fleets of the Ming Dynasty come to mind. They sent out their voyages six times, traveling around the southeast Asia and the Indian ocean (to India, Arabia, east Africa, and Iran). They had varying degrees of prior contact with many of those they visited, but further out as they went further west and south they only knew the routes. Other than some minor anti-piracy activity, overthrowing a Sri Lankan king who was engaging in piracy against Chinese trade partners in favor of an ally, and helping an ally in Indonesia (in Sumatra) reclaim their throne from an usurper, it was primarily peaceful and mutually beneficial on all sides. Gifts and tribute were exchanged, and ambassadors and samplings of goods from previously known but not directly contacted regions returned with the fleets.

There is also history of peaceful trade (probably with no real reason for conflict) between Indonesians (Makassans) and pre-colonial, aboriginal Australian societies.