Brunei, Malaysia and Indonesia are the 3 countries that make up Borneo. Borneo is also an island.
Borneo is in southeast Asia. Borneo is an island, but not a country. It actually has 3 countries on it. Brunei is completely on it. Indonesia and Malaysia both have parts of their countries on it. See the map below.
Three countries.
Two island, Borneo with Malaysia. Papua with PNG
Malaysia, Brunei, and Indonesia all have land on the island of Borneo.
Three countries share the island of Borneo: Malaysia, Indonesia, and Brunei.
Thailand and Borneo.
Borneo
Indonesia, Malaysia, and Brunei share the island of Borneo.
3 countries occupy parts of the island Borneo. Indonesia (most of it), Malaysia and Brunei.
USA & Borneo,
The Island of Borneo has three sovereign nations with territory on it. Brunei, Malaysia and Indonesia.