When Lam Kwing-tong discovered he had Covid-19 antibodies in his bloodstream in late February, it came as a shock given his lack of symptoms. The 56-year-old dentist’s diagnosis at a quarantine camp in Hong Kong’s Sha Tin district, however, was only the culmination of an experience he now says was like “living in hell.”Lam and his wife, Lau So-kuen, were among 364 Hong Kong residents on board the Diamond Princess cruise ship, where 712 people were infected and eight died, three Hong Kong…