The commander of the Rapid Deployment Force said yesterday that he has requested an outpost for his trouble-shooting force somewhere on the ground in southwest Asia.

Lt. Gen. Robert A. Kingston told a Pentagon news conference that he had recommended to the Joint Chiefs of Staff five countries where a staff of 150 could keep an eye on Persian Gulf activities and coordinate military planning.

"Negotiations are taking place at this time," Kingston said. But the three-star Army general declined to say what countries he had in mind. Other sources said that Oman, right on the strategic Persian Gulf, is high on the wish list.

Kingston called the recent Bright Star operation, in which 6,000 American troops maneuvered in the Indian Ocean area, a success. The exercises in Egypt, Somalia, Oman and Sudan cost $69 million. Kingston said that getting enough water to troops in the desert in southwest Asia is still one of the biggest problems.

The Rapid Deployment Force is the umbrella name for several units, including Marines and the Army's 82nd and 101st airborne divisions, which could be sent to trouble spots in the Persian Gulf in a hurry. The RDF's main mission would be to protect oil fields in southwest Asia.

Kingston said he would prefer to store equipment for the RDF on land bases in the area rather than on ships as planned, but "so far we have not been invited in" to store equipment in a country in the area.

Asked if the RDF is really a paper outfit that could do little to stop a Soviet thrust in the Persian Gulf area, Kingston replied, "Given adequate strategic warning, we can get sufficient force to accomplish the mission."