Human Trafficking: Child labour and the forced prostitution is a big problem in Thailand. Women and children from poor families are the major targets, particularly those from the Northern Hill tribes who lack official citizenship. Sex tourism forms a large part of the informal economy. Not only is sex slavery a major abuse of human rights, but also causes a large public health risk by the transmission of HIV and other STI's.
Natural disaster: Tropical storms, flooding, droughts, landslides and earthquakes are frequent events in Thailand due to its equatorial placement and position on tectonic plate boundaries. Disaster Risk Reduction is currently a top priority for the government, however political inefficiencies due to unrest have slowed the implementation of much needed infrastructure.
Homelessness and Street Children: Many youth and children live on the streets in Thailand due to neglect, domestic violence, poverty or natural disasters. In order to survive they often turn to theft, begging, prostitution, drug dealing or child labour where they are exploited and abused, as the informal economy offers no legal protection or financial security.
Sources:
CIA WorldFact Book - https://www.cia.gov/library/publications/the-world-factbook/geos/in.html
Hman Trafficking Organisation - http://www.humantrafficking.org/countries/thailand
ReliefWeb - http://reliefweb.int/country/tha