In Southeast Asia, there was a large slave class in Khmer Empire who built the enduring monuments in Angkor Wat and did most of the heavy work. Between the 17th and the early 20th centuries one-quarter to one-third of the population of some areas of Thailand and Burma were slaves. By the 19th century, Bhutan had developed a slave trade with Sikkim and Tibet, also enslaving British subjects and Brahmins. According to the International Labour Organization (ILO), during the early 21st century an estimated 800,000