Three men are alleged to have exploited two 17-year-old boys from Cardiff, who were arrested in Thailand in June after being found with 64kg of cannabis concealed in their suitcases while attempting to return to the UK.
The teenagers remain in custody in Thailand.
Levi Coomansingh, 20, Patrick O’Driscoll, 30, and Gareth Press, 42, all from Cardiff, appeared at Cardiff Magistrates’ Court on Friday charged with drug offences and conspiracy to arrange travel for the purpose of exploitation.
Nicholas Evans, prosecuting, said: “This case involves an organised criminal network operating between the UK and Thailand.
“It is alleged that teenagers were trafficked to Thailand to act as drug couriers.”
Coomansingh, of Butetown, faces charges of conspiring to fraudulently evade a prohibition on the importation of a Class B drug and four counts of conspiring to arrange travel for the purpose of exploitation.
O’Driscoll, of Caerau, faces similar charges as well as possession of a firearm.
Press, of Ely, has been charged with conspiring to evade a prohibition on the importation of a Class B drug and two counts of conspiracy to arrange travel with a view to exploitation.
The three men appeared together in the dock and were not asked to enter pleas.
Magistrate Peter Welsh said: “These matters have to go to Cardiff Crown Court.
“Your next appearance will be on September 4th.
“You will be remanded in custody.”
A fourth person, Ffion Bowes-Cavanagh Hooley, 24, of Caerau, has been charged with conspiring to evade a prohibition on the importation of a Class B drug and concealing criminal property.
She was granted conditional bail and will also appear at Cardiff Crown Court on September 4.
A spokesman for South Wales Police said: “The children remain in custody in Thailand where they are being supported by their families and the Foreign and Commonwealth Office.
“The families have been updated regarding the arrests and charges.
“We understand this continues to be a concerning time for them and the wider community.”
In June, South Wales Police was made aware that two 17-year-olds from Cardiff had been arrested in Thailand. The force subsequently launched an investigation into the circumstances which led to the children travelling to the country.
A 23-year-old man from Keighley, West Yorkshire, was also arrested on suspicion of improper importation of controlled drugs and is on police bail.
