Today he is a renowned poet, musician - and now author. His debut novel Narcopolis, about the lives of people in an opium den in 1970s Bombay, in India, has been shortlisted for this year's prestigious Man Booker Prize.
"Life isn't always beautiful; sometimes it's horrible," says the Indian-born Thayil, 52, who went to secondary school in Hong Kong. "I'm lucky to have a second chance. It's like I've come out of a bad dream."
Thayil, back in the city last week to attend the Hong Kong Literary Festival, admits: "I was a dangerous kid. At 14, I began to take drugs, and it went on for a long time - as long as I can remember."
After finishing Form Five at a local school in Hong Kong, he enrolled at a renowned international secondary school. He says: "I often went to these parties with my schoolmates after midnight.
"We'd be passing around drugs and smoking. Sometimes, I'd sneak out of my house and meet my friends at a park in the Mid-Levels and do the same."
Once he had started using drugs, he was hooked. He took heroine and also drank heavily. Sometimes he would take them together.
His drug addiction lasted for almost three decades until he finally managed to quit, at 42.
"People often ask me why I did it and I wish that I had the answer," he says. "I did well in school and my parents are good to me. I had no excuse really.
"Thinking back, perhaps, I was in a hurry to grow up; I wanted to be an adult - and quickly."
What saved him, he says, was his family and their never-failing support. "When things became really bad, I'd go back to my parents' home, lock myself up in the room and tell them not to let me out until I was better. They've always been there for me."
The other thing that kept him going was work. Unlike many drug addicts, who are usually jobless, he has never stopped working as a journalist in India, Hong Kong and New York. He says: "I covered it [my drug taking] well and never missed a deadline. The heroine didn't affect my ability to think, though it made me suffer a lot of physical pain. As long as I could tolerate it, nobody knew."
However, he regrets the "lost" years and opportunities because of his drug taking. "I wasted a great deal of time - more than half of my life," he says.
"Now, I have a lot to make up for; I want to leave a few very good books behind."
He has already started work on his second novel, which he hopes to publish after Christmas.
Now his life is an open door to positive possibilities, instead of the dead-end street of his past. "When I wake in the morning and start writing, I feel happy and optimistic," he says. "Writing is healing - like prayers."
Jeet Thayil took part in the 2012 Hong Kong International Literary Festival, which ends on Sunday.
For more details, go to www.festival.org.hk