Beth Henley talks about her way of writing plays

She looks like a college graduate in need of a job. Small, thin, with a braid trailing down her back and stumping about in a rumpled cardigan, flannel skirt, and hiking boots, Beth Henley looks like anything but the prizewinning playwright that she is. She talks in a Mississippi molasses drawl only slightly tempered by her years in Los Angeles, and she still cringes with embarrassment about the publicity photographers who snap her picture during lunch.

''Oh, gosh, it's so embarrassing. People run up afterward and say, 'Who are you? Who are you?' I just tell them I hired that guy to take my picture while I eat.''

This remark is typical of this Southern-born actress-turned-playwright who is as much a crazy quilt of contradictions and oddball eccentricities as her Pulitzer Prize-winning play, ''Crimes of the Heart'' - an unusual but fetching tale of three slightly wacky Delta sisters reunited when one of them shoots her husband because ''she didn't like his looks.''

One critic termed the play ''a collision between Chekhov and Carson McCullers.'' New York Times critic Mel Gussow said Miss Henley ''finds humor even in violent acts.''

''Well, there's a tension that sets up with danger,'' she tries to explain when asked about her unorthodox sense of humor. ''Like in the old '[I Love] Lucy' shows. You know, you wonder, is she going to get caught in the candy factory or slip on the banana peel? It's tense but funny.''

Curled up like a kitten here on the couch in the lounge of Boston's Shubert Theatre, Miss Henley is in town to launch the premiere touring production of ''Crimes of the Heart,'' which is still playing on Broadway. It was her first full-length play (she wrote a one-act one during college), and in addition to the Pulitzer Prize, it won her a New York Drama Critics' Circle Award in 1981. She was 27 at the time, and the first woman to earn the Pulitzer Prize for drama since 1958. How does she feel about that?

''Oh, I don't know,'' she moans. ''People always ask me that and I never come up with a good answer. Happy. Surprised. Good, I suppose.'' She concludes with a shrug and a tug on her braid.

Sitting with this playwright, who has been hailed by critics as part of a new and impressive generation of woman dramatists, one finds her more child than successful and wealthy playwright. ''Crimes of the Heart'' was sold to Hollywood for a reported $1 million, and Miss Henley now owns a house in the star-studded Los Angeles residential area of Laurel Canyon, a far cry from her Southern upbringing as one of four daughters of a lawyer-father and actress-mother in Jackson, Miss.

But all that success pales in the face of the pixieish person sitting here. Completely at home in her baggy schoolgirl clothes and ponytailed hair, she scrunches around the couch, scratches her leg, and squints and scowls her expressive face with abandon. She confides she likes doing Jane Fonda exercises, surfcasting, and going to David Bowie concerts. During a conversation she will lapse into different characters and voices - imitating people, making pouncing gestures with her hands, or pretending to play the piano - anything to drive home her points. It is not difficult to tell that she used to be actress. ''No, I still do acting,'' she corrects her questioner. ''It keeps me in touch with my imagination.''

That imagination, which percolates to the surface with such disarming regularity, is apparently what feeds the creative fires of this writer.

''Well, I just start with an idea of what I want to write about, like a funeral [''The Wake of Jamie Foster'']; a beauty contest [''Miss Firecracker Contest'']; or somebody in the family getting thrown in jail [''Crimes of the Heart'']; and then I do a lot of thinking about the characters who are in the event and what happened to them before that. Then when I actually sit down to write the play it just comes real fast, almost like automatic writing.''

She says that she does little reworking of her plays and that she tries to write every day - getting to her downtown Los Angeles office around noon, lying on the floor or a rose-colored chaise longue, and writing out her plays in longhand.

Since ''Crimes of the Heart'' debuted at the Actors Theatre of Louisville in 1979, Miss Henley churned out ''The Wake of Jamie Foster,'' which met a quick demise on Broadway earlier this year, an unproduced screenplay called the ''The Moon Watcher,'' and her latest venture, ''The Debutante Ball,'' a play she says is not yet in production and is ''even darker and more violent'' than ''Crimes.'' ''Those are just the images I get,'' she says; ''they're not really a conscious choice.''

Jon Jory, director of the Louisville theater, where ''Crimes'' won the 1979 Great American Play Contest, says Miss Henley is more of a serious student of theater than she appears. ''Theater history courses really meant something to her. She obviously loved Chekhov and really thought a lot about how those effects could be achieved.''

Certainly her plays are peopled with characters whose bizarre bumpkinry is straight out of the Southern gothic tradition. They tread a fine line between unbelievable caricature and poignant reality. One director said of her work, ''It's because she writes for herself that her plays come out so true.''

It's a sureness of vision that shines through the works of this woman who insists that she would ''probably still be working in the parts department of TRW'' if she hadn't stumbled into playwriting after a mild success with her one-act ''Am I Blue,'' written while still attending Southern Methodist University.

''She seems all glow and sparkle,'' says Mr. Jory, ''but she is very firmly attached to her point of view. She's like a good piece of flint. You can strike sparks off her.''

Those sparks are no more in evidence than when she is pressed about why women are just now gaining recognition in the creative fields. Suddenly the gawky little girl disappears, she sits up straight, and her voice is firm. ''Well, picture not going to college. Picture tons of kids. No way to earn a livin' . . . , not being able to vote. Think about that. People pretend that life is like the commercials. And it's not.''

Life, she says, can be difficult, even terrifying, in its smallest moments. This is why she writes the way she does - chronicling the strange and often grotesque events of real life, but always tempering it with compassion and humor. As her character Lenny states in the concluding moments of ''Crimes of the Heart,'' ''A vision just sort of came into my mind . . . something about the three of us smiling and laughing together . . . it wasn't forever; it wasn't for every minute, just this one moment and we were all laughing.''