Teao Tsi-sheng, a 41-year-old Malaysian national, Somchai Nantanoi, 31, and Jane Amnatsan, 46, were presented at a news conference by Provincial Police Region 9 deputy chief Chaovalit Sawangphuet at Hat Yai police station on Friday.
The trio allegedly colluded with four others to abduct Lee Hsi-huei, a 60-year-old seafood businessman, from Hat Yai airport for ransom on Feb 16.
Mr Teao, the alleged gang leader, was said to have contacted Lee by phone to lure him to fly from Malaysia to Hat Yai. The victim was then taken from Hat Yai to a shelter in a forest in tambon Padang Besar of Sadao district, said Pol Maj Gen Chaovalit.
The perpetrators then contacted Lee's relatives in Malaysia and demanded 8 million baht to secure his release.
The relatives negotiated with the gang and agreed to bring 1.5 million baht in ransom to a meeting point at the entrance of Soi Kachorn Uthit in tambon Kuanklung of Hat Yai district.
After the money was handed over, the kidnappers did not release Lee. His body was later found buried in tambon Kukud of Sathing Phra district on Feb 20.
Police arrested Mr Somchai and Mr Jane at their houses for questioning. Their accounts then led to the arrest of Mr Teao at a Toyota service centre in Hat Yai.
Police also seized two pickup trucks, believed to have been used in the kidnapping, and five mobile phones, including one belonging to the victim.
The four other accomplices remain at large, and police were quickly gathering evidence to seek arrest warrants, said Pol Maj Gen Chaovalit, adding that officers already knew who they were.
Police have pressed charges of abduction, premeditated murder and concealing a body against the three arrested men, who admitted to committing the offences, he added.