It seemed harmless enough last winter when little Alex Silverman started asking his mother for extra money to buy packs of Pokemon trading cards, the children's craze that has swept schoolyards and stationery stores across the country.

Six months and more than $2,000 later, however, his mother, Janet, is convinced that her 9-year-old son's new hobby is no ordinary passing fad but a real threat to his welfare -- and to her wallet.

In what could bring at least a smile, if not some remuneration, to millions of other concerned moms and dads, Mrs. Silverman and another Merrick mother have signed up with a team of class-action lawyers on both coasts to charge that the Pokemon craze constitutes a form of illegal gambling no less addictive than scratch tickets or slot machines.

As only the childless need to be told, Pokemon (derived from the Japanese words for ''pocket monster'') cards are about the same size as baseball cards but carry the images and describe the special powers of dozens of imaginary creatures and monsters with names like Alakazam, Blastoise and Charizard. A pack of 10 or 11 sells for $5 to $8.