The Securities and Exchange Commission, which operated for much of last year without its full allotment of five members, will soon be short one member again. Moderate Republican commissioner James C. Treadway Jr. announced Jan. 9 that he would leave the SEC this spring, two years before the expiration of his term. That leaves the commission with two Republicans and two Democrats -- and the prospect of deadlocks on some issues.

Treadway, a corporate lawyer, has supported enforcement actions against corporations involved in financial fraud. In the same speech in which he announced his departure, Treadway warned the accounting profession that it needs to correct the "present public perception that much about accounting is fundamentally flawed" if it hopes to regain the public's confidence.

Treadway suggested several ways in which the SEC could deal with abuses. He said it could stop efforts by executives to shop around for an accountant who will let questionable items pass. It could crack down on sham transactions, the year-end doctoring of the books that often is a prelude to the company's sudden collapse. He also predicted that the SEC would be more involved in bank accounting matters in the future.

Treadway called on the accounting profession to police itself, and impose sanctions in individual cases. And he predicted that the public would demand that the commission and the accounting industry work to ensure that there are no cases in which accountants failed to uncover problem companies, despite the costs that are sometimes involved. He added that his predictions were based on intuition, rather than inside information about the SEC's future actions. Moreover, commissioners on the lecture circuit speak for themselves rather than the SEC. MORE VIEWS . . .

In a Chicago speech the same day Treadway was speaking, commissioner Charles L. Marinaccio recommended prohibiting bidders from making hostile offers to buy a portion of a company's stock. He said this would help right the balance that he feels has shifted away from the target company in favor of the bidder.

He also called for outlawing "greenmail," which he described as "a polite term for extortion." Greenmail is the practice of paying a bidder above-market prices for his stock to make him disappear. Marinaccio said those who purchase blocks of shares should be prohibited from selling the shares back to the company within a certain period of years.

Marinaccio also denounced the concept of waiver-by-conduct, in which foreign investors in U.S. markets would be obliged to reveal the same information that domestic investors must in SEC investigations of insider trading.

"Implicit is the arrogance that the U.S. market is so enviable that the foreigners will be forced to comply with our requirements regardless of their historical sensibilities," he said. The commissioner predicted that waiver-by-conduct would adversely affect the flow of capital into this country. Instead, he suggested that an international structure be provided for the world equities market similar to those that exist for international finance or trade, such as the General Agreements on Tariffs and Trade. REQUIREMENTS FOR BROKER-DEALERS . . .

The commission plans to review net capital requirements for broker-dealers to decide whether to make fundamental changes in the SEC's existing rules. Firms are required to keep certain reserves on deposit in special bank accounts to be used in case of liquidation to pay off money they owe customers. Among the issues to be decided are whether all firms, large and small, should use the same standard of liquidity, and whether firms that do not have customer accounts should have to maintain such strict standards. PERSONNEL CHANGES. . .

The Office of Public Utility Regulation, headed for many years by Aaron Levy until his retirement Jan. 18, has been moved into the Division of Investment Management, which is headed by Kathryn B. McGrath. William Weeden will be responsible for the office's daily operations.