On your birthday, you're supposed to be allowed to do and say just what you want. So, today, on the eve of the 50th Masters golf tournament, 29-year-old Seve Ballesteros let out the shaft all day, pulling pranks on the stuffy Augusta National course, making brave prognostications and tongue-lashing PGA Tour Commissioner Deane Beman.

At the 16th hole, the mischievous Spanish virtuoso delighted the crowd by deliberately skipping two-iron shots across the pond until he put one next to the flag. "It made the people happy," said Ballesteros.

After his round, Ballesteros all but said he would win his third green coat of the 1980s. "I know this course as good as my house," said Ballesteros, an emotional, streak player who has twin aspirations: honoring the memory of his father, who died last month, and embarrassing Beman, symbol of his controversial suspension from the PGA Tour this season. "I come to this place to enjoy the hospitality and to win the Masters -- that's all. I feel strong mentally and physically. I am ready to win."

Ballesteros then criticized the Masters patriarchs for tampering with the ninth and 18th greens (easing their frightening slopes) and for not offering nearly enough invitations to European stars. "I am very surprised we are only three from Europe . . . You know, we are quite good. Look who won the Ryder Cup last year [beating the United States]. . .[The Masters] is very, very short on invitations. It is very difficult to show your ability if you never get the chance." Ballesteros then named a dozen players he thought might well deserve to be in this field of 88.

Finally, to cap off the day, Ballesteros reached a crescendo in his criticism of Beman, calling him, "A little man who wants to be big. Let's forget Deane Beman. The Masters is more important than Deane Beman."

Ballesteros, who continued to critique Beman at length, even intimated a possible vendetta, saying, "He has had problems with me in the past. Maybe this suspension is a good chance for him to do something against me that will make him happy."

To be a PGA Tour member, a player must appear in at least 15 tournaments in the U.S. or else be suspended for a year. Ballesteros admits that this rule, instituted before the 1984 season, was written expressly to satisfy him and induce him to join the Tour. In 1984, Ballesteros played in 15 events. In 1985, however, he only played in nine. As Tom Watson said today, "Seve broke a rule that was written for him and by him."

The result: he will only play in four U.S. events this year: the Masters, U.S. Open and PGA (which have no PGA Tour affiliations) and the USF&G Classic in New Orleans two weeks ago, where he was defending champion.

Although the letter of the law is almost certainly against Ballesteros, the spirit of the law may be in Ballesteros' corner. The game's court of public opinion definitely is split.

"I don't know why I am suspended," he said today. "It is a joke . . . Every week, they have new rules. It is more difficult to follow the rules on the PGA Tour than to win the Masters," said Ballesteros. "There are two things I will never understand. Why is [Isao] Aoki [of Japan] different? He only played eight tournaments in the U.S. last year but he is not suspended. And why does Beman say that he cannot accommodate the rules for one person? . . . That's a lie. He accommodated Aoki."

Aoki clearly falls through a loophole in the Tour's regulations -- an exotic distinction between what constitutes a player's "home circuit" and his "home country." What it boils down to is that Ballesteros was unlucky enough to be born in a country that has only three professional golf tournaments, while Japan has many. Aoki gets "releases" that allow him not to play in U.S. events -- releases for which Ballesteros is not eligible because of his nationality.

Most of the Ballesteros-Beman dispute is about precedent and ego -- the power games that go on between the competing golf tours of Asia, Europe and America as well as Ballesteros' well-documented love of special treatment.

When Ballesteros wasn't taking on Beman, defending Masters champion Bernhard Langer was bemoaning his fate in his squabble with the IRS. Under a new law that is pending, foreign golfers would have to pay taxes on their world-wide income if they spend more than 121 days in the U.S. The current rule is 182 days.

"I'll only be able to play in 14 events," said Langer, who doesn't want to wake up one day in the 70 percent bracket. "I know that's not 15 [to satisfy the Ballesteros Rule], but I hope the PGA Tour will not penalize me [in 1987]. I don't want to be disposed of [like Ballesteros]. I think I have showed that I want to play over here."

As if all this weren't enough, several other issues seem to be on every tongue here.

*Will Augusta's native son, Larry Mize redeem himself after his last-mile collapse in the Tournament Players Championship?

*Will Curtis Strange, who blew last year's Masters on the final nine holes, get revenge?

*Will Calvin Peete, No. 2 on the money list in 1986 and the Tour's most frequent winner the past four seasons, become the first black to win the Masters?

*If Jack Nicklaus, who's been atrocious all season ($4,404), doesn't show some life in the '86 majors, will he seriously consider retiring? Nicklaus only concedes, "I still enjoy competitive golf . . . but, obviously, I don't enjoy playing golf the way I've played it this year."

*Finally, does Mac O'Grady, who despises the Masters almost as much as he dislikes Beman, have some kind of stunt planned? O'Grady (who faces the possibility of $15,000 in fines and two months in suspensions for his criticism of Beman) has told intimates that, if he has a tap-in to win the Masters, he will refuse to putt out until . . .

Until what? Nobody knows. Not even Ballesteros, who has become O'Grady's fast friend. "Mac O'Grady is a nice man, a gentleman," said Ballesteros whimsically.

As evening approached here at mild Augusta National, where the azaleas never have been prettier or the weather forecast more blissful, no one was more full of good cheer than Ballesteros. "They will change the rules sooner or later," Ballesteros said confidently.