THE EASY THING is to read the story of Soviet defector Arkady Shevchenko's spending spree as a modern day "Ninotchka." And, in fact, it is always good for a belly laugh whenever a prominent public figure takes a fling, especially a Russian going wild in the West. The CIA inadvertently added to the comedy by giving Mr. Shevchenko a stipened "to help him along until he becomes established in his own identify." Since one of the ways Mr. Shevchenko chose to seek his identify was to tour the Virgin Islands with a well-paid female escort, one may ask what sort of identity the agency had in mind for him.

But the comedy really ends there. The original stories had the CIA looking like a sugar daddy at one remove, but it is doubtful that the agency paid Mr. Shevchenko the sums of money if took to fly off to the Caribbean or to buy this woman a car. Mr. Shevchenko had a good deal of his own money. And it is less interesting that some of the CIA stipend went to fund his spree than that he chose the form of a spree in which his "own identity" was to be found.

On the whole, Mr. Shevchenko's spee has but two sides, neither of which is funny at all. The first has to do with the nature of a defector generally, who is by definition a walking identity crisis. Not only is a defector despised by the country he disowns, but he is also distrusted by the country he adopts, which inevitably regards him - despite the jubilation of his crossover - as a traitor in character and, possibly, a double agent. This was true of Yuri Nosenko, who claimed to have known Lee Harvey Oswald before the assassination of President Kennedy and who for nearly three years was grilled and virtually held a prisoner by the CIA. Mr. Shevchenko's comparative freedom is undoubtedly a comment on the unimportance of his information, his reliability, or both.

The second side of Mr. Shevchenko's spree is purely personal. And there we may only guess why the man who six months ago was U.N. undersecretary general for political and security affairs - he's the highest ranking Soviet defector ever - chose to "establish" the kind of new identity that makes him out a fool. It may be that Mr. Shevchenko is having an identity crisis, or whatever term we choose for a breakdown of control. Such things are only funny to those who have never been there.