The House Administration Committee approved a $300,000 budget yesterday for an in-depth study of U.S.-South Korean relations.

In acting on Rep. Donald Fraser's (D-Minn.) request earlier in the day, the House Administration Accounts Subcommittee turned aside arguments by Rep. Edward J. Derwinski (R-Ill.) that the investigation would be too costly and should be scaled down.

Fraser asked for $356,700 for the first year of his international relations subcommittee's 18-month inquiry. But noting that two months of the year had already passed, the House committee budget overseers agreed on a $300,000 figure, the same level of funding as Fraser's request.

Derwinski, ranking minority member of Fraser's subcommittee, said after the vote that he felt his objections led the Accounts Subcommittee members to question Fraser more closely, "to see that Don did feel some constraints."

The Fraser subcommittee budget is expected to get final House approval next week, along with other House committee budgets. His investigation will focus on activities of the Korea Central Intelligence Agency in this country, as well as South Korean lobbying efforts aimed at U.S. government agencies, and the academic, media and business worlds.

The House ethics committee already has received preliminary approval to spend $530,000 for an investigation of reports that South Korean agents tried to influence some members of Congress with cash and gifts.

Rep. Lee Hamilton (D-Ind.), a member of both committees investigating South Korea, appeared with Fraser yesterday to testify that the two inquiries would not overlap.

The mood of the Accounts Subcommittee was made clear when Rep. John Brademas (D-Ind.), the majority whip, told the other subcommittee members that he supported Fraser's request - and added that House Speaker Thomas P. (Tip) O'Neill did, too.