A Russian man has been arrested and illegal drugs seized from his room in Hua Hin town of Prachuap Khiri Khan province.
The arrest followed the seizure of a parcel containing 840 grammes of mephedrone on June 24.
Customs officials found that the parcel sent from Poland contained capsules filled with light brown powder. The substance was sent for laboratory testing, which confirmed it to be mephedrone, an illegal drug.
Mephedrone can be used as an ingredient for a synthetic stimulant known as bath salts.
An investigation led to the arrest of the Russian man when he came to pick up the parcel on Friday.
Police searched his room and found many types of drugs in small quantities. They included methamphetamine, MDMA, ecstasy, LSD, cocaine, ketamine and mephedrone.
Police said the man was responsible for collecting parcels containing drugs sent from abroad. They were stored in his room before being delivered to other locations.