Duch reached the border of Thailand in May 1979. Details of his whereabouts at this time remain unclear. It is believed that he went to the forests of Samlaut where he was reunited with his family. Here Duch was demoted by Brother Number Two, Nuon Chea, for having failed to destroy the documents at Tuol Sleng. At the border, he learned to speak Thai and taught himself English. He later taught English and mathematics at a refugee camp in Borai just inside Thailand.