Ambiguity of what is Sa Huỳnh culture puts into question its extent of influence in Southeast Asia. Sa Huỳnh culture is characterized by use of cylindrical or egg-shaped burial jars associated with hat-shaped lids. Using its mortuary practice as a new definition, Sa Huỳnh culture should be geographically restricted across Central Vietnam between Hue City in the north and Nha Trang City in the south. Recent archeological research reveals that the potteries in Kalanay Cave are quite different from those of the Sa Huỳnh but strikingly similar to those in Hoa Diem site, Central Vietnam and Samui Island, Thailand. New estimate dates the artifacts in Kalanay cave to come much later than Sa Huỳnh culture at 200-300 AD. Bio-anthropological analysis of human fossils found also confirmed the colonization of Vietnam by Austronesian people from insular Southeast Asia in, e.g., the Hoa Diem site.