Here's a story to warm the heart. A couple of years ago a Thai family opened a tiny storefront restaurant, the Thai Derm, on a side street in Silver Spring. Business was poor at first, but the family persisted.

They scrubbed and polished so that even the modest little dining room was pretty, they kept on serving very good Thai dishes at very low prices, and they gave their customers caring service. Gradually word of mouth prevailed, and now all nine tables are occupied nearly every night. (You'll need a reservation on weekends.)

Has success spoiled the Thai Derm? Not at all. The staff is as sweet as ever, the food as good, the prices as low.

What to expect? The usual Thai appetizers, lots of noodle dishes, some unusual offerings, a few nightly specials. Begin with soup. Shrimp with lemon grass soup is a delight, simultaneously hot and tart. Even better is the velvety chicken with lemon grass soup, with coconut milk, ginger and kafir lime leaf. For something milder, try the pork soup, with a rich, garlicky broth and good meatballs. Or the duck soup, beautifully flavored and generously endowed with meat that's still on the bone.

Among the appetizers, the spring rolls are crackly skinned and lightly fried, as are the chicken wings stuffed with crabmeat. And both come with dynamite sweet-hot dipping sauces. A hotter appetizer is the excellent larb with rough-ground beef, sweet onion, fresh mint, lemon juice and chili pepper.

Perhaps the best entree in the house is pad khing -- marinated beef, pork or chicken with mushrooms and chunky scallions in a marvelous sauce that combines chili pepper, shredded ginger, sugar and garlic. Also outstanding is a specialty of the house called guey teow Thai derm, an unusual mixture of rice noodles with roast pork, crisp-fried pork skin, and wonderfully subtle fish cake and fish balls, all sprinkled with crushed peanuts. It adds up to a lovely combination of mild flavors, and it comes with an optional, fiery-hot broth. Have it with the broth on the side, to be spooned over the mixture to taste.

Another winner is the Thai omelette, a big portion of flawlessly fluffy egg filled with ground beef, peas, chunky fresh tomato, onions and carrots, in a mild, slightly thickened sauce.

Vegetarians can do very nicely here. Many of the noodle dishes are available without meat, and the vegetables are cooked beautifully so they're lively but not raw. Sweet and sour vegetables are particularly good, with zucchini, onion, green pepper, tomatoes and mushrooms, in a tart, not-too-sweet sauce.

The noodle dishes are not uniformly successful. We've found the "gravies" generally thick and bland, and in one case -- the wonton with egg noodles -- the dish was mushy and devoid of zip.

For dessert, don't miss the home-made coconut ice cream when they have it, and the dense, cake-textured Thai custard, made with coconut, lotus seed and brown sugar.