Open for lunch Monday through Friday 11:30 a.m. to 3 p.m.; for dinner Monday through Thursday, 5 to 10 p.m., Friday and Saturday to 10:30 p.m., Sunday to 9:30 p.m. Reservations suggested. DC, MC, V. Prices: Most appetizers and entrees $4 to $7. Complete dinner with wine or beer, tax and tip about $10 to $18 per person.

On our first visit to this new Thai restaurant we took a friend who'd recently returned from an extended stay in Europe. "If this place were in Paris," he observed, "it would be terribly chic, everyone would go, and they'd charge an arm and a leg." Luckily for us, Georgia Avenue isn't Boulevard St.-Germain, so there are no crowds to worry about at the Gulf of Siam (not yet, anyway), and the prices are so low you'd think inflation didn't exist. Even better, the look of the place belies the bargains: you get soft lighting, fresh linens, handsome table settings, some pretty Thai artifacts and thoughtful service.

As the name implies, there's a lot of seafood here, and much of it can be marvelous. But there are almost as many nonseafood items among the 60 or so choices on the menu, and there are jewels among these, too. (More can be found on the nearly hidden blackboard next to the bar, which lists daily specials.)

To begin with, a warning. Many Thai dishes are fiery hot with chili pepper, sometimes enough to make Szechuan cooking seem like an ulcer diet, and the Gulf of Siam doesn't modify its seasonings to suit non-Thai tastes. If you don't specify, you'll get the full, clear-your-sinuses treatment. But you can order the hot dishes "mild," which will be just pleasantly hot for most people. And many dishes are nonpeppery to begin with. (Note, by the way, that the dishes printed in red on the menu aren't necessarily the hot ones -- they're "chef's specialties.")

As is the Thai custom,, appetizer portions are virtually as large as entrees, and they run about the same price. Among the peppery-hot ones, yum nua (No. 15) features tender beef slices beautifully marinated in lemon juice, with sweet red onions, cucumbers and minced garlic -- a dish of delightful flavor and texture contrasts. Pla nua (No. 16), just as good, uses scallions, lemon grass and fresh ginger with the beef. Two marvelous dishes, but unless your palate has calluses, be sure to order them "mild."

For an appetizer that's mild to begin with, there's a nice, if unremarkable, rendition of the traditional moo sate -- pork marinated in a sweet sauce, grilled and served on skewers for dipping in a peanut sauce. Then there's that other Thai-Vietnamese standard, spring rolls, which have been good on some nights, overngs, in which chicken wings are pulled inside out, stuffed with minced crab meat and fried. A clever trick, and nicely executed here, but once you've gotten over trying to figure out how they do it, what's left is actually a pretty dull dish. A couple of other mild ones: shrimp tempura, a $4.95 bargain that's good but not exceptional; and spareribs, in a delightful, peppery, garlicky sauce. (Some of the ribs are too fatty, but at $3.95 for a generous plateful, all is forgiven.)

Never pass up the soup at a Thai restaurant. At the Gulf of Siam, some are merely very good, like shrimp with lemon grass or bean thread and minced pork -- a rich chicken broth with rough-ground pork, fresh garlic and scallions. And some, like chicken galanga, are ambrosial, with coconut milk that plays off perfectly against lemon grass and chicken.

What may be the best entree in the house is also a phenomenal bargain, but it's not always available. It's a big clay pot in which have been steamed the biggest portion of mussels we've ever seen -- we stopped counting after the first 30, and there were still plenty to go. The mussels were absolutely fresh and the flavoring was a heavenly blend of the mussel broth, lemon grass, lemon juice, some galanga, and just enough green chili pepper to add a little pep.

Flounder is not usually an exciting fish, but its preparation here is so impeccable that it can become a rare treat. The best way to have it is steamed in a good fish stock with some black beans for a touch of saltiness (No. 34). It's good fried, too, in a wonderful sweet-hot-garlicky sauce (No. 33). Be aware, though, that there's sometimes a little quality-control problem with the flounder -- one night we had a sweet-and-sour version that was very good but nearly all bones. And avoid the occasional catfish special, which suffers from too much of an overoily sauce.

Noodle dishes are excellent, and the best of them is pad thai (No. 55), an irresistible combination of soft noodles, crisp bean sprouts and scallions, plump shrimp, lovely bits of fried egg, just enough chopped peanuts for a little crunch and flavor, and a sweet but not cloying sauce. A delicious rib-sticker, and only $4.25.

Vegetables, too, are outstanding, with the combination vegetable platter (No. 48) one of the best anywhere. The vegetables are cooked so that they retain their life and crunch, and the slightly sweet, slightly salty sauce plays up their natural flavors rather than overpowering them. If you want meat or fish with wonderful vegetables, try the dishes in which chicken or shrimp are combined with red and green sweet pepper, onion, scallions and cashews (No. 28 or 39) -- a bit of sugar in the sauce combines deliciously with the onion.

A few more delights: the sweet and sour sauce, more tart and less cloying than most, and best had with shrimp or scallops; the mild garlic and white pepper sauce, which is good with just about everything; and the Thai basil sauce, with its slight taste of licorice, best with chicken or pork.

For dessert, be ecumenical: pass over the Thai creations and order Irish coffee. The tableside preparation is a production number and it makes a soothing close to dinner.

Before the Gulf of Siam opened a few months ago, Wheaton already had two excellent Thai restaurants. Does three make too many? Is there too much gold in Fort Knox?