In June 1986, Duch was sent to China to teach as a Khmer language expert at the Beijing Foreign Language Institute. He returned to the Thai-Cambodian border a year later and changed his name to Hang Pin. He worked as a senior bureaucrat just inside the Cambodian border at Pol Pot's secretariat at Camp 505. Shortly after the Paris agreement in October 1991, he moved with his family to the small isolated village of Phkoam close to the Thai border. Here he purchased some land, and began teaching in the local school. He was known as a good teacher, but one with a fiery temper.