Why has Thailand launched crackdown on prostitution amid arrival of 5,000 US soldiers?

Thai authorities launched a crackdown on prostitution amid arrival of around 5,000 US soldiers in Thailand. Prostitution is illegal in Thailand, but it's still visible in Bangkok and Pattaya. There's a risk of sexual exploitation and the spread of sexually transmitted diseases with the heavy influx of US personnel. Reports of soldiers' stress and suicide attempts have added another concern.