Open daily, 11 a.m. to 10 p.m. No credit cards. Reservations.

Food: Thai food, complex and exciting

Style: Pretty touches in a simple setting

Price: Most appetizers $3, most main dishes $3.50.

WESTERN COOKING deals with the four taste variables - sweet, sour, salty, bitter - one at a time, occasionally combining two and maybe three. Herbs and other fragrances are usually added in simple combinations, pepper in judicious amounts. Eastern cooking, particularly that of Southeast Asia, frequently combines sweet-sour-salty-bitter in one dish, introducing strands of several fragrances and explosions of pepper at the same time. The remarkable thing is that the resulting flavor is not muddied; the nuances swirl and intermingle, remaining a rainbow rather than blending into gray.

That is what Thai food can taste like - a rainbow of sensations on the tongue and in the nose, the hottest varieties sending smoke signals long after they have been tasted.

And that is what the food at the Siam Inn tastes like. What is even more notable is that is 110 appetizers and main dishes can combine sweet-sour-salty-bitter in so many distinct manners. Return to the menu several times, taste a dozen dishes, and entirely new sensations remain to be discovered on the tongue.

To start - logically - with soup, a milky white gai tom kha (chicken with a herb called lemon grass and a root called galanga in coconut milk) mutes the fire of green chilies with the faintly sweet coconut milk so that first you smell its sweetness and perfume, then you sip the smooth, peppery broth, finally to bite into tender chicken. The theme is varied with fish instead of chicken, or no coconut milk but more lemon tartness. Unfortunately, the soups without lemon grass - stuffed cucumber or bean thread and pork in chicken broth - are bland by comparison.

Sink your teeth heavily into appetizers at the Siam Inn, the choice being from among thirty-three. The two most common among Washington's Thai restaurants - skewered beef satay and fried stuffed chicken drumsticks - are here no match for the well-favored Thai Room. But one more familiar in Chinese restaurants - the delicate dumplings called shiu mai - are here even more delicate and delicious than usual. And unfamiliar territory yields the greatest rewards; try a salad of sliced barbecued steak with tang of lemon grass, bite of chili pepper, crunch of scallion and fragrance of garlic. Or sample an oniony salad with tender steamed hog maw, or a crisp meaty dish of deep fried hog maw permeated with sweet pickled ginger. The appetizer salads - thin transparent noodles with dried or fresh shrimp, chicken or pork, and various combinations fo crisp raw chopped vegetables, herbs like coriander and plenty of tart lemon and salty fish sauce - serve as appetizers should, to awake and tease the taste buds. There are also Thai versions of egg rolls, but more fragile and flaky, the filling more dense and bland.

Appetizers are large at the Siam Inn, meant to be shared among several people. Main dishes, on the other hand, are about the same size as appetizers (and similar price, as well), meant to be mixed with rice. They are highly seasoned, so if you enjoy searing your internal organs, let the waitress know. If not, ask for restraint with the heat. In any case, with the choice of main dishes so extensive and the prices averaging $3.50, you may want to order an extra main dish or two, despite the waitress's awe at American appetities. Some of the dishes - duck, chow foon noodles - are adaptations from Chinese cuisine, and taste adapted. The waitress can help you through the forest of choices, but above all, order something - chicken, pork, beef or (the best of the lot) fried ox tongue - with garlic and pepper. It is not fiery; rather, it is astonishingly savory, the fried garlic and white pepper working magic on the meat. For more intense heat, try peppery chicken, beef or pork, the meat cut into tiny bits and fried with Asian basil and garlic, with a few spoons of subtle brown sauce that grows on you. Then there is stuffed pork in oyster sauce, a surprise of a dish that is glistening under a red-brown glaze, the pork stuffed with a highly perfumed chopped meat and sliced into beautiful cross sections and laid atop still crisp Chinese broccoli. Fish at the Siam Inn comes deep-fried or sauteec, a delicious choice being a whole fish buried under ginger, black beans, and a julienne of pork and vegetables in a thin brown gravy. Thai food includes curries, outrageously hot and as thin as soups, their colors ranging from red to gold. To contrast with peppery dishes, be sure to include pad Thai, soft rice noodles tossed with bits of crisp pork and dried shrimp, slightly sweet and peanut flavored.

In all, what you will find with the food at the Siam Inn, besides wanting more of it the next day, is that the vegetables are inevitably crisp, the sauces thin and starch-free, the flavors intricate and the perfumes intense. Even the tea is fragrant.

All this is served with an emphasis on graciousness, though the single waitress I saw would be overwhelmed by a full house. With a little Eastern patience, one can enjoy the mystery of Asian food in a setting prettied by silk parasols suspended from the ceiling and elaborate miniature paintings, brightened by red banquettes and blue tablecloths, livened by soft Thai music. As of this writing, the restaurant had not yet received its liquor license, but there were hopes of having by now Thai beer to suit the food. Also, desserts were limited to canned tropical fruits such as lychees and toddy palm. But the Siam Inn is still evolving. Considering that it has started with exciting food, low prices and thoughtful service, its fortune cookies should be promising a bright future.