Botanical name: Hydnophytum moseleyanum
Common name: Ant Plant
Family: Rubiaceae
Origin: Southeastern Asia
The caudex is hollow, and forms a perfect nest for the ants, which protect the plant, and gets home and sweet sap in exchange.
Similar plants: Hydnophytum moseleyanum (Ant Plant)
Link to this plant:
https://toptropicals.com/catalog/uid/hydnophytum_moseleyanum.htm