"They were not from one body but were in small pieces. They have been sent for forensic examination to confirm if they were from babies who died after delivery or in the womb," Police Major General Chawalit Prasopsin told AFP News on Sunday (16 November).
While scanning the package, a Bangkok parcel company discovered the body parts that included a baby's head, several feet and "sheets of skin," with one confirmed to be of an adult bearing a large tattoo.
The body parts were kept preserved by filling the containers with formaldehyde solution.
According to Chawalit, the presence of the solution is indicative of the parts being for "a collection or for educational purposes".
Police are still investigating the origins of the parcel and details of the exact final destination in the US are yet to be disclosed.
Local media sources, however, are saying the parcel was addressed to a location in Las Vegas, Nevada.
A similar package was discovered in 2012 in the luggage of a British citizen of Taiwanese origin. In that instance, Thai police had discovered six human foetuses that had been roasted and covered in gold leaf in accordance with a black magic ritual.
Preserved foetuses are believed to bring good fortune to the owner in Thai black magic rituals.