Ruth Brubaker of River Bend, returning to the Washington golf scene after a four-year absence, shot a net 71 yesterday to take a two-stroke lead at the halfway point of the 49th annual Keefer Cup tournament at Chevy Chase.

Brubaker's husband is in the State Department and was stationed in Malaysia where it is hot and steamy the year round and only the privileged are permitted to ride carts. So yesterday's warm whether was no great hardship for Brubaker, who carries a 12 handicap and scored a gross 83.

The low gross for the day went to Congressional's Pam Smyth with an 82, 11 over women's par. The best nine-hole score of the day was turned in by Chris Epperly of Army Navy, a newcomer to this tournament, who had 39 on the front side.

Defending champion Betty Looney of Army Navy was safety in the qualifying fold with a net 78. The low 32 and ties qualified, bringing to 35 today's field for the final 18 holes.

Tina marlowe of Woodmont, one of the younger players in the Women's District Golf Association and a former Middle Atlantic junior champion, had a gross 87 for a net 80. Carol Davies of Washingtonian, who carries a five handicap, the lowest in the tournament, came in with a gross 84.

Brubaker was out in 41 and home in 42. She started with a bogey on the first hole and a double bodey on the second when she three-putted. But after that her putter had a great touch.

She parred six straight holes from the seventh through the 12th, thanks to some long putts.

Smyth had a 42-40, with her only birdie coming on the short fourth hole when she sank a 15-footer, Jean Pohanka, also of Congressional, had a first nine of 41, with a birdie on the long third when she put a wedge shot a few feet from the pin. But she faulted on the back with a 46 for an 87 and a net 73. CAPTION: Picture, Pam Smyth, By Margaret Thomas-The Washington Post