Thomas J. Ball was a super-salesman. For several years, he ran a booming, one-man investment counseling business, Tom Ball & Associates, in Northern Virginia. Dozens of clients, many of them military and government workers, gave him their life savings, thousands of dollars, to invest in deals he called "safe and fully guaranteed."

Yesterday, Ball, 39, appeared in U.S. District Court in Alexandria and pleaded guilty to five felony charges in which he admitted that his investment counseling scheme was a fraud.

A government prosecutor told the court that the lucrative land development and securities deals Ball boasted of to his clients were nonexistent -- elaborate ruses devised by Ball to cheat investors out of their money.

All told, Assistant U.S. Attorney Joseph J. Aronica told the court many area investors lost thousands of dollars they intended to use for such purposes as their retirement and their children's education.

In the years when Ball's business thrived, he enjoyed the good life. He and his wife drove an expensive Mercedes 450 SL sedan.He built a $200,000 home on five well-manicured acres in Great Falls. And he took frequent trips to posh vacation resorts. In one two-year period, he traveled to Hawaii, Bermuda, Venezuela and St. Maarten, an exclusive Caribbean island resort.

All the while Ball, who told his clients he was their "personal adviser," showered them with financial planning notebooks, "full binding contracts" and tape recordings full of impressive-sounding investment tips. Ball promised some investors he would triple their money. He also prepared wills and had himself listed as executor for some of his clients' estates.

By mid-1979 Ball's "house of cards began to collapse," according to his attorney, Darwyn H. Lesh. The fraud indictments followed and led to Ball's appearance yesterday before U.S. District Judge Albert V. Bryan Jr.

Ball, asked by the judge to comment on prosecutor Aronica's summary of the government's case against him, responded, "What he said happened; it did happen."

Ball spoke in a low voice. He wore brown slacks and a black and white sport shirt, which seemed to contrast with the affluent, confident image that investigators said he presented to prospective investors.

Lesh told reporters that, contrary to investigators' suspicions that Ball has a fortune stashed away, his client is now broke.

"The money was in fact spent," Lesh said. Ball's Mercedes has been repossessed. His family must move out of the Great Falls home, which has been foreclosed. Ball is behind bars.

The charges to which Ball pleaded guilty yesterday were two counts of mail fraud, one of securities fraud, filing a false income tax return and lying to the grand jury that probed his operation.

In exchange for his pleas, the government agreed to drop the rest of the charges in the 21-count indictment against him.

Judge Bryan postponed sentencing until June 6. Ball could be sentenced to up to 23 years in prison and a $21,000 fine.

He was jailed earlier this week when a Fairfax Circuit Court judge revoked his bond after he pleaded guilty to a state false pretense charge for swindling a Fairfax County man out of $20,000 in the investment scheme. Sentencing has been postponed in that case, too, although Ball has agreed to in a plea bargain to accept three years in prison and make restitution of $10,000.

Typical of the investors in Ball's scheme was Peter Schoeffel, a U.S. Navy captain who lost $83,000, according to the indictment against Ball, most of it in back pay and interest accumulated while he was in a North Vietnamese prisoner of war camp.

The wife of another investor said yesterday she was glad to hear of Ball's conviction. "We had felt the law was only made for criminals," said the woman, whose husband is one of about 30 investors who have unsuccessfully sued Ball to recover their money. The woman, who asked not to be identified, said Ball made off with the $55,000 she and her husband had saved in the 19 years of their marriage.