賒 is clearly defined as “delaying payment for something” in Chinese dictionaries; it commonly appears in the phrase “賒帳”, which has a similar meaning.
賖 is a Chữ Nôm used to write “xa” in Vietnamese, which means “far”. To me, it seems like 賖 is a corruption of 賒, since 賒 is pronounced like “xa” as far as I know. On the other hand, there is no entry for “賖” in Chinese dictionaries, and might be a Vietnamese innovation. However, that would also be weird since its pronunciation is markedly different than other characters which also have the 余 component.
余- dư 餘- dư
Has 賖 ever been used in Chinese? Is it related to 賒?
EDIT: AFAIK, 賖 is also used for xơ, but this sound also doesn’t come close to the expected pronunciation.