Medicine can cut risk by 90 percent, but it's not approved for prevention

Thailand has been a hot destination for Chinese tourists for years. Yet many now are heading to the Southeast Asian country for a new reason - to buy cheap drugs to prevent HIV.

Pre-exposure prophylaxis, commonly known as PrEP, is a type of medicine that, if taken daily, can reduce the risk of HIV infection via sexual intercourse by more than 90 percent, according to health studies.