He has created new identities for many people. An expert at crafting fake passports, the man, known as "the Doctor", has helped drug dealers, criminals and terrorists move freely across borders. Thai police have called his forged passports the "best on the market". Now behind bars in a Thai prison, the Doctor is speaking out for the first time, revealing the secrets of his trade in this exclusive interview. "My job could fool the immigration and any agent in the airport and pass through, no problem," he boasts. For years, he operated in the shadows in Thailand. International security experts say the country is a hub for transnational crime, bringing the Doctor a steady flow of criminals who want new identities. "Even his customers didn't know who the Doctor was. He was able to hide in Thailand for 20 years," says Major-General Surajade Dhammadamrong. "Each person in his network didn't know each other, making sure they never met. Criminals operating like that are very hard to track down." But authorities eventually closed in on him as part of a crackdown on passport forgers. He may now be behind bars, but the Doctor is not yet ready to give up all his secrets - Thai authorities concede his true identity remains a mystery. 101 East traces the hunt for the master forger.