Thai agencies working as part of the Airport Interdiction Task Force made the arrests following a September 12 tip-off about a New Zealand man set to receive drugs to smuggle home, The Nation reported.
With police on surveillance, Rein allegedly asked hotel staff to arrange a taxi ride for him on Saturday while he was waiting for "friends" in his room.
Emeka and Wararat allegedly arrived that afternoon with the briefcase and all three people were arrested when they returned to the lobby.
A Ministry of Foreign Affairs & Trade (MFAT) spokesperson said the NZ Embassy in Bangkok had been in contact with local authorities regarding the arrest.
"For privacy reasons we are unable to provide further details," the spokesperson said.