Soonthorn Dejavichitlert, co-owner of Washington's Thai Taste restaurants on Connecticut Avenue and in Georgetown, has three simple explanations for the popularity of Thailand's cuisine: "It's not very fattening, not very expensive . . . and it's a challenge."

"People want to know how much they can handle" in terms of heat and spiciness, the restaurateur explains, conceding that some of his customers can eat whole the incendiary chili peppers that help give Thai food its sting.

And it's never boring, he adds, noting the versatility of Thai staples: "Broccoli can be used with chicken, pork, oyster sauce or black bean sauce"; similarly, shrimp can be mated "with lemon grass, steamed with Thai herbs, saute'ed with red chilies" or paired with a curry sauce for completely divergent tastes. Indeed, Dejavichitlert's menu lists almost 90 dishes, not an uncommon number for a Thai restaurant.

His and several other Thai restaurants will offer examples of Thai specialties at today's observance of Kao Pansa, an annual celebration marking the beginning of a three-month Buddhist Lent. The daylong celebration at Wat Thai center in Silver Spring begins at 7 a.m. with a breakfast for the center's monks, to be followed by a Thai sermon (12:30), a children's classical dancing demonstration (2 p.m.) and open food stands (9 a.m. to 3 p.m.). Proceeds from the food sale will benefit Wat Thai, a nonprofit Buddhist temple and community center at 9033 Georgia Ave.

Charcoal-grilled chicken, a traditional, if somewhat mild Thai dish, is one of several Dejavichitlert will offer the public. The recipe uses ingredients readily available in grocery stores, though a list of several Thai markets has been included for cooks who might wish to indulge themselves in supplies of lemon grass, shrimp paste or tamarind. For this simple dish all you'll need on hand before heading for the express lane of your supermarket are sugar, salt, oil and a grill.

Express Lane list: chicken, garlic, peppercorns, curry powder, sherry wine, shallots, Chinese parsley root (optional), rice THAI TASTE RESTAURANT'S CHARCOAL-GRILLED CHICKEN (3 to 4 servings)

Dejavichitlert adds 3 or 4 Chinese parsley roots to the marinade in this recipe, but the vegetable can be omitted.

3 1/2- tO 4-pound chicken

3 cloves garlic, peeled

1 teaspoon black peppercorns

1 tablespoon curry powder

1 1/2 teaspoons sugar

1/2 teaspoon salt

2 tablespoons vegetable oil

2 tablespoons sherry wine, or more to taste

3 shallots

3 to 4 Chinese parsley roots (optional)

Rice for serving

Wash the chicken under cold running water and pat dry; cut into pieces and set aside in a flat dish.

Combine the garlic, peppercorns, curry powder, sugar, salt, oil, sherry, shallots and parsley root, if using, in a blender or food processor and blend until well incorporated. Add more sherry if mixture is too thick. Pour contents over chicken, cover with foil, and marinate overnight.

Before serving, place marinated chicken on a grill and cook just enough to retain juiciness -- the meat should not be overcooked.

Serve with rice, if desired.

Area Thai markets include: uangrat, 5888 Leesburg Pike, Alexandria, 578-0622.

Bangkok 54, 3832 Mount Vernon Ave., Alexandria, 549-8488.

Thai Market, 902 Thayer Ave., Silver Spring, 495-2779