A psychotherapist who counselled drug abusers and rehabilitated them for about five years fell prey to drugs himself.

Gopal Mahey, 33, did not just take drugs, but even loaned money to a man he was counselling so they could sell drugs together. He thought of it as an "investment opportunity". And he did this while he was counselling drug abusers in jail.

He was nabbed after he dropped a pouch with drugs as he was leaving Changi Prison in December 2013.

Yesterday, he was given eight years' jail with seven strokes of the cane, having pleaded guilty earlier to one charge of drug trafficking and one of drug consumption.

In her brief grounds of decision, District Judge May Mesenas said: "The role of counsellors is critical, especially those who help drug addicts... to rebuild their lives and relationships which were once destroyed. (Gopal) had such laudable intentions."

"However, they were clearly thwarted by the greed and lure of profits which came from drug trafficking. Regrettably, the person whom he sought to help fight the battle against drugs... would be the very person whom he led astray," she added, referring to Gopal's accomplice.

In 2009, Gopal joined the Centre for Psychotherapy and obtained a master's in professional counselling. The centre was contracted by the Singapore Prison Service to counsel inmates with drug problems.

Separately, in 2013, Gopal became friends with See Hui Chuan, alias Andy, 37. He counselled See for personal problems and they would also smoke methamphetamine or "Ice" together. Gopal found out See had contacts he used to sell drugs to, and was in need of money.

Said Deputy Public Prosecutor Rajiv Rai: "The accused then decided to loan (See) $5,000 on two separate occasions to support his drug trafficking activities... (Gopal) saw it as a good investment opportunity."

Gopal's returns would be $300 cash per month; 1.25g of Ice per week; and five slabs of Erimin-5 per month. He even collected a consignment of drugs for See and handed it to him on Dec 19, 2013.

The next day, at about 5pm, Gopal dropped a pouch while he was leaving Changi Prison. An auxiliary police officer found the pouch, which contained an unknown pill and a packet with a crystalline substance.

Closed-circuit television footage showed Gopal dropped the pouch. He was caught by the Central Narcotics Bureau three days later and his urine tested positive for methamphetamine. See was arrested later that day, and has been dealt with.

When contacted, the Singapore Prison Service said it conducts stringent checks on all individuals entering its prison institutions.

Gopal, who left his job in January 2014, could have been jailed for up to 20 years with 15 strokes of the cane for his trafficking charge. He could have been jailed for 10 years and fined $20,000 for his drug consumption charge.