A New York lawyer, who allegedly made a killing in the stock market by using information about undisclosed financial plans of his corporate clients, agreed yesterday to reimburse persons who sold him stock.

Alternatively, if the seller cannot be located, the attorney agreed to give to charity whatever is left of his profits, reportedly amounting to $33,742.

The unique settlement was announced simultaneously with the filing of a suit against the lawyer by the Securities and Exchange Commission.

In the suit, filed at U.S. District Court here, the SEC accused David H. Hall, president of the New York firm of Demas & hall, with violating the anti-fraud provisions of the federal securities laws.

While neither admitting not denying the SEC allegations, Hall accepted the court order barring him from further violations of the anti-fraud laws.

It's unusual for the SEC to file suit against a lawyer.

But the case reportedly marks the beginning of a wide-ranging crackdown by the SEC's enforcement division against self-dealing by corporate insiders.

Hall was retained by a number of large corporations as a "special shareholder relations" counsel, according to the SEC suit.

Hall's corporate clients included Conchemco, Kansas City Southern Industries, Pioneer Western Corp., and Great Lakes Dredge & Dock Co.

On March 22, 1979, Conchemco, Lenaza, Kan., manufacturer of mobile homes, discussed retaining Hall in connection with the company's plans to make a tender offer for some of its own shares.

Through meetings with executives, Hall learned the company planned to acquire some 41 percent of its own stock, at between $24 and $28 a share, about one-third above the market price at the time.

Hall bought some 5,000 shares of Conchemco's stock at between $15.50 and $21.25 a share. Then, two days after the company announced the tender, the attorney sold 1,000 of the shares for $26 a share, according to the SEC suit.

In the case of Great Lakes (now a wholly owned subsidary of Great Lakes International Inc.), Hall bought 1,000 shares of the stock on Oct. 14, 1977, at $47 a share. As an adviser to the company, the SEC alleges that he knew that on Oct. 25, the company board of directors would declare a 100 percent stock dividend and an extra cash divadend of $1.40 a share, in addition to its regular quarterly dividend of 35 cents a share.

According to the SEC suit, Hall profitably bought and sold stock in St. Louis-based Laclede Steel Co., thanks to inside information.

For example, when he learned that Laclede would project a 400 percent increase in earnings for 300 shares at $65.75 a share before the news was made public. When it was, the stock quickly climbed to $83 a share.