The Senate Appropriations Committee yesterday approved a $15.6 billion supplemental funding bill for the rest of this fiscal year that is triple the size of an earlier House version, mainly because it includes $8.4 billion requested by the administration for the International Monetary Fund.

The bill, approved by the committee as Congress left town for its Memorial Day recess, is scheduled to go to the floor June 8, which will be just after the Senate returns.

Although the appropriation exceeds President Reagan's request by about $600 million, including funds for the troubled Environmental Protection Agency and other domestic and foreign programs, committee Chairman Mark O. Hatfield (R-Ore.) said he believed it would be acceptable to the president.

In terms of money, the major difference between the $15.6 billion Senate bill and the $4.8 billion measure passed by the House Wednesday was the $8.4 billion to help the IMF ease the international debt crisis. The House bill did not include the IMF money.

The Senate committee insisted on certain conditions, however, including a requirement that the United States vote in IMF deliberations "to prevent the buildup of industries in foreign countries which cause damage to American producers and manufacturers and thereby cost American jobs."

But, at the request of administration officials, it abandoned a requirement that the United States oppose loans to countries "whose policies are totally contrary to U.S. interests."

In terms of congressional politics, the more important difference between the two bills had to do with a House proposal for a limit on outside earnings by senators, which the Senate committee unceremoniously scrapped.

Under a House-Senate agreement last year, House salaries were raised from $60,662 to $69,800 and outside earnings were limited to 30 percent of salary or roughly $18,000. Senate salaries were kept at $60,662 but an earlier limit on outside income was removed.

This year, following reports that 13 senators received $50,000 or more last year from honoraria for speechmaking, mainly to special interest groups, the House approved a rider to the appropriations bill to limit senators' outside earnings to 30 percent of salary as well.

Senate committee members considered retaliating against the House for this by such means as repealing the House pay raise, but finally contented themselves with knocking out the proposed outside earnings cap.

On other issues, the committee rejected attempts to cut $30 million from its allocation of $50 million in military assistance to El Salvador and to end multiyear contracting for the controversial B1 bomber.

It approved, without dissent, $454 million to continue production of Pershing II missiles, planned for deployment in Europe in December. This amounted to the same slight reduction from the administration's request that the House approved a day earlier.

The committee also rejected a House-proposed prohibition on further coal leasing on government lands, with Democrats indicating they would hold off their fight over the issue until the Senate debates the bill.

Although controlled by Republicans, the committee rejected the administration's request for $20 million for its "Project Democracy" propaganda campaign abroad. The Democratic House had approved $15 million for the effort.

For the Environmental Protection Agency, the committee approved additional funds totaling $11.1 million, compared with $6.8 million approved by the House. The administration had requested no additional funding for EPA.