Except as provided in subsection 6, payment of a service retirement benefit shall begin on the first day of the month following the month in which the qualifying member becomes eligible to receive payment of the member's service retirement benefit under section 18451 or 18507. A full month's benefit shall be paid to the beneficiary or estate of the recipient for the month in which the member dies. A qualifying member may select payments in one of the following methods. [1989, c. 95, §16 (AMD).]