Dozens gathered at Vaiola Hospital in the morning including Mark Santos from the New Zealand High Commission’s office in Nuku’alofa to farewell the deceased.
Mr Cook, 67, died on Sunday after being allegedly assaulted on Friday night on the outskirts of Nuku’alofa.
According to a Kaniva News report, Police said the accused, who was arrested on Sunday, remains in custody.
The Ma’ufanga teen has not been named and is due to appear in court on Monday.
Mr Cook ran the Salvation Army’s alcohol and drug awareness centre.
His death shocked the Tongan community with many saying this was a great loss for Tonga in its fight against drugs abuse.
RNZ correspondent in Nuku’alofa, Kalafi Moala, told the radio Mr Cook was “one of Tonga’s warriors” in the fight against drug abuse and addiction.
“We, here in Tonga, are very shocked by the death of Ned,” Moala said.
“The big question is…who is going to be filling his shoes? He was not only a leader in dealing with drug addiction and so on, particularly meth, but basically he was the only trained [drug] counsellor in Tonga who was trying to deal with the problem,” Mr Moala said.