Passport validity
Count six months from the date you intend to enter Papua New Guinea
ICA's current General FAQ says that a passport must be valid for at least six months from the date you intend to enter Papua New Guinea. This is the clearest current rule to use when checking whether a passport is suitable for travel.
If the passport is close to expiry, renew it before applying where possible. A visa or entry permit cannot safely be planned around a travel document that may no longer meet the entry-validity rule on the date of arrival.