Happy to Be Ill (Situational Irony)
When Salvatore is diagnosed with rheumatism, instead of lamenting his poor health, the young man is overjoyed. In this instance of situational irony, Salvatore receives what would otherwise be bad news as good news because his debilitating condition means he will be discharged from the navy and sent home to his family and his fiancée.
Salvatore's Fiancée Won't Marry a Man in Poor Health (Situational Irony)
Although Salvatore is overjoyed that his health condition means he will return home to his fiancée, upon his return he learns that she refuses to marry a disabled man. In this instance of situational irony, Maugham undermines Salvatore's and the reader's expectations by making the reason he can return to his fiancée the same reason she refuses to see him.
Foreigners Think Salvatore Is Lazy (Dramatic Irony)
After describing Salvatore's exhaustive work schedule of nighttime fishing and daytime vine cultivation, Maugham's narrator notes that Salvatore's rheumatism pain often becomes so intense that it prevents him from working. On those days, he lies on the beach and smokes cigarettes. The narrator comments that foreign tourists see Salvatore and assume he is merely being lazy. In this instance of dramatic irony, the reader knows Salvatore is far from lazy, and is in fact very hardworking, even with his disability.