Each foreign accident and health insurance company doing business on the assessment plan in this state shall keep deposited at all times with the commissioner one regular assessment sufficient in amount to pay the average loss or losses occurring among its members in this state during the time allowed by it for the collection of assessments and payment of losses. No such company may be licensed by the commissioner unless it keeps and maintains with the commissioner for the protection of persons to whom it may become obligated at least ten thousand dollars in bonds of the United States, of the state of North Dakota, or of political subdivisions within this state, or in mortgages on improved and unencumbered real estate within this state worth double the sum loaned thereon and approved by the commissioner.