Pol Colonel Adis Charoensawat, deputy commander of Narcotics Suppression Division 3, said the two Chinese nationals were arrested on a road in Tambon Rai Khing in Samphran district of Nakhon Pathom province at 1pm on Monday.
The two were identified as Jun Di, 42, and Jia Li Xia, 28.
They were charged with being in possession of Category 1 narcotics with intent to sell and collaborating to smuggle the drug out of the kingdom.
Adis said officers from his division investigated and traced the two after Customs officials at Suvarnabhumi Airport detected suspicious parcels. Officials checked and found the drug hidden in between layers of PVC boards that were used to make boxes of bottle openers.
The two denied knowledge of the heroin, saying they were hired to send the parcel.
Police later checked their residence and froze assets worth 9.37 million baht, including two condominium rooms in the Ratchadaphisek area, worth 4 million baht, a condominium room in Sathorn worth 2.5 million baht, and two Pattaya condo rooms worth 2 million baht.