In 1977, the Khmer Rouge began internal purges directed at those suspected of disloyalty. Hun Sen, who had risen to the rank of Battalion Commander, became paranoid and fled with his followers into Vietnam where they joined a rebel army and replacement government organized by the Vietnamese in advance of its effort to overthrow the Khmer Rouge regime. Bun Rany, who was left behind, was imprisoned by the Khmer Rouge and would not see her husband again until almost two years later when the Vietnamese invaded Cambodia in 1979. Upon defeating the Khmer Rouge and occupying Cambodia, the Vietnamese named Hun Sen as Deputy Prime Minister and freed Bun Rany who then began organizing orphanages and schools for the orphans left behind by the genocidal policies of the Khmer Rouge. In 1985, Hun Sen was appointed Prime Minister, giving Bun Rany a better platform to expand both her economic activities and her humanitarian work. During the post-1988 process of Thai-Cambodian rapprochement, she forged a close personal relationship with the wife of Thai Prime Minister Chatichai Choonhavan, and became deeply involved in the rapidly growing legal and illegal trade between Cambodia and Thailand. From her position as first lady, she began to call attention to the plight of those infected with HIV/AIDS, the poor and women's issues. In April 1994 at the first congress of the Cambodian Red Cross, she was elected as its Vice President while Princess Eng Marie, wife of then Co-Prime Minister Prince Norodom Ranariddh was elected president. At its second congress in 1998, Bun Rany was elected President after Hun Sen consolidated his power by violently ousting and exiling Ranariddh.