Is it permissible for a retired man who receives a pension and supports a family to work another government job and receive its salary, knowing that the country's law prohibits dual salaries?

As long as the government contract does not permit receiving two salaries, it is not permissible to take them, and one must choose the more suitable of the two. An exception to this is extreme necessity, where the salary is not sufficient to cover basic needs; in such a case, other work is permissible only to the extent that it alleviates the necessity.