If any of the health care services which are promised in any such agreement are not to be performed by the health care service contractor, or by a participating provider, such activity shall not be subject to the laws relating to insurance, provided provision is made for reimbursement or indemnity of the persons who have previously paid, or on whose behalf prepayment has been made, for such services. Such reimbursement or indemnity shall either be underwritten by an insurance company authorized to write accident, health and disability insurance in the state or guaranteed by a surety company authorized to do business in this state, or guaranteed by a deposit of cash or securities eligible for investment by insurers pursuant to chapter 48.13 RCW, with the insurance commissioner, as hereinafter provided. If the reimbursement or indemnity is underwritten by an insurance company, the contract or policy of insurance may designate the health care service contractor as the named insured, but shall be for the benefit of the persons who have previously paid, or on whose behalf prepayment has been made, for such health care services. If the reimbursement or indemnity is guaranteed by a surety company, the surety bond shall designate the state of Washington as the named obligee, but shall be for the benefit of the persons who have previously paid, or on whose behalf prepayment has been made, for such health care services, and shall be in such amount as the insurance commissioner shall direct, but in no event in a sum greater than the amount of one hundred fifty thousand dollars or the amount necessary to cover incurred but unpaid reimbursement or indemnity benefits as reported in the last annual statement filed with the insurance commissioner, and adjusted to reflect known or anticipated increases or decreases during the ensuing year, plus an amount of unearned prepayments applicable to reimbursement or indemnity benefits satisfactory to the insurance commissioner, whichever amount is greater. A copy of such insurance policy or surety bond, as the case may be, and any modification thereof, shall be filed with the insurance commissioner. If the reimbursement or indemnity is guaranteed by a deposit of cash or securities, such deposit shall be in such amount as the insurance commissioner shall direct, but in no event in a sum greater than the amount of one hundred fifty thousand dollars or the amount necessary to cover incurred but unpaid reimbursement or indemnity benefits as reported in the last annual statement filed with the insurance commissioner, and adjusted to reflect known or anticipated increases or decreases during the ensuing year, plus an amount of unearned prepayments applicable to reimbursement or indemnity benefits satisfactory to the insurance commissioner, whichever amount is greater. Such cash or security deposit shall be held in trust by the insurance commissioner and shall be for the benefit of the persons who have previously paid, or on whose behalf prepayment has been made, for such health care services.