The four – Ibrohem Hawae, 40; Nuratasanim Useng, 23; Nurulhuda Wamae, 18; and a 16-year-old male – were charged with illegal possession of illicit drugs with intent to sell.
Twenty-six packages of heroin, weighing 10.4 kilogrammes, and a pickup truck with Bangkok licence plates were seized, police said during a media briefing on Saturday.
The arrests were made after police and soldiers manning a checkpoint on Phetkasem Road in tambon Khaochaiyarat of Pathiu district stopped a suspicious pickup truck for a search on Friday. The search found heroin hidden in a secret compartment of the vehicle. The drugs were worth at least 15 million baht, local media reported.
Authorities said that Ibrohem, the driver, confessed to having smuggled the drugs from Mae Sai district in Chiang Rai for delivery to Sungai Kolok district near in Narathiwat.
The suspects had made two earlier deliveries before being caught, said Pol Lt Gen Sorasak Yenprem, chief of Provincial Police Region 8.
Police said the suspects confessed that the first delivery earned them a profit of 5 million baht and the second one 10 million. They shared the profits with an agent who invested the money, officers said.
Local media reported that Ibrohem had recently been released from jail where he had served a sentence in connection with the murder of security officers in the deep South.
Police said theywould coordinate with the Fourth Army to interrogate the suspects to find out whether they had any link to the southern unrest.