H. Joe Selby, senior deputy comptroller of the currency for bank supervision, on Sunday became acting head of the agency that supervises the nation's 4,700 banks.

A 31-year veteran of the Office of Comptroller of the Currency, Selby temporarily replaces C.T. Conover, who resigned at midnight Saturday. The administration has not named a successor to Conover, whose adamant advocacy of banking deregulation made him one of the most controversial comptrollers of the currency.

Selby said that although certain decisions will have to await the appointment of a new comptroller, he does not intend to put the agency in neutral. He said that there is a great danger that an organization could "get into a state of inertia waiting" for a new executive and that he intends to make decisions.

"We will continue the projects we have running, come up with new ones and revisit one that we're already doing," Selby said.

He said key issues the agency will deal with in coming weeks include developing more comprehensive and mandatory disclosure requirements for nationally chartered banks and revising the supervisory approach to banks to refocus the agency's priorities on risks to the banking system rather than to specific banks.

Selby said the agency will require banks to disclose to shareholders information about their business, assets, legal actions pending against them and regulatory actions taken against them. The banks will have to disclose comparative financial data for the last three years. He said the banks also will be required to inform their customers once a year in writing that disclosure statements exist and will be provided upon request.

He said the revised supervisory approach will attempt to marshal the agency's resources to deal with eight levels of risk to the banking system. The highest order of priority will be issues that present risk to the entire banking system, "whether they are real estate loans, energy loans or even agricultural loans. We ought to be able to focus on system risk and denote it," Selby said.

He said the next priority is the giant multinational banks, which individually could shatter the banking system, followed by regional banks and then the unstable and stable smaller banks, which presumably provide the least danger to the banking system.

Selby, 53, has been a senior deputy comptroller since 1975 and has held his current title since 1983. He said he plans to retire in a year-and-a-half, when he turns 55.

ISAAC REMAINS . . . Although Conover resigned as comptroller before the Reagan administration named a successor, Federal Deposit Insurance Corp. Chairman William M. Isaac has promised that he will continue serving until a successor is sworn in. L. William Seidman, dean of the business school at Arizona State University and economic adviser to then-President Gerald R. Ford, appears to be the leading candidate for the position. But President Reagan has yet to nominate anyone for either the comptroller's job or the FDIC post.

FDIC REBATES . . . The FDIC has rebated $67.5 million, or about 5.1 percent of the $1.3 billion in premiums that banks paid last year to insure depositors' accounts up to $100,000. In 1983 the rebate was equal to 13.5 percent of total assessments. Five years ago, before the FDIC faced a tide of failures, banks regularly received rebates of 50 percent or more of premiums they paid. The basic premium is one-twelfth of 1 percent of total deposits. With the rebate, the FDIC said banks paid two-twentyfifths of 1 percent of their deposits last year and one-fourteenth of 1 percent in 1983.

The insurance agency not only insures deposits and becomes receiver when an insured bank fails, it also supervises about 9,000 state-chartered banks that are not members of the Federal Reserve System. The FDIC's losses and expenses last year were $1.2 billion, of which $750 million represented losses on loans and other assets it took over from failed banks.

NEW FACE . . . Robert F. Miailovich has been named associate director of the FDIC's division of bank supervision for planning and program development. Miailovich has been with the agency since 1963 and had been assistant director for failing banks and assistance transactions.