South Korea has joined Thailand, Singapore, India, and other Asian nations in the lucrative business of medical tourism. The number of foreigners coming to South Korea for medical care is still a fraction of those getting treatment in India, Thailand, and Singapore, industry officials said. But clinics and the South Korean government are trying hard to attract these tourists, who not only bring in money for cash-strapped hospitals but also help the economy by staying after their procedure is over. The South Korean government has revised immigration rules to allow foreign patients and their families to get long-term medical visas and altered laws to permit local hospitals to form joint ventures with foreign hospitals in some cases.