Any person who keeps, operates, or exhibits a pool or billiard table on which the public can play, whether for pay or not, outside of an incorporated city or town having a police force shall, on conviction, be fined not less than $50 nor more than $100 for each table and may also be sentenced to hard labor for the county for not less than 30 days nor more than 50 days. This section shall not apply to clubs conducted by companies which provide welfare work for their employees; nor shall it apply to pool or billiard tables kept or operated at any military camp of the United States or within one fourth of a mile of such military camp, nor to pool or billiard tables kept and operated at any nitrate plant or on any land acquired and held by the United States.