Klong Khong beach on the southern Thai island of Koh Lanta is a long sweep of coarse silver sand fringed by Indian almond trees and palms. A knot of beach shacks offer tourist staples—massages, fruit shakes, grilled seafood—in signs written in English and, in similar prominence, Mandarin Chinese. Yet few Chinese faces grace Koh Lanta these days as fallout spreads from the coronavirus outbreak that has so far infected more than 60,000 people and claimed at least 1,360 lives.