It is just after noon, and the restaurant is empty on what's supposed to be the busiest day of the year - Christmas. Owner Peter Fong isn't worried.

Catering to synagogues the night before had nearly emptied the shelves at his Singapore Kosher Vegetarian Restaurant on Race Street near 10th in Chinatown, so Fong had to make a quick shopping trip to get ready for the crowd he knew would come.

As Christians gather with family to mark the holy holiday, a Jewish tradition also plays out: going to the openings of new movies and eating at Chinese restaurants. It is a ritual born of necessity - Chinese restaurants and theaters are among the few places open on Christmas.

Fong's restaurant is a favorite among the Philadelphia region's Jewish community, thanks to its kosher status.

"Christmas Eve and Christmas Day are the best time of the year," says the 55-year-old Fong, a native of Malaysia, who came to the United States around 1989.

Soon after Fong opened a vegetarian restaurant in Philadelphia, he met a rabbi who taught him about the mystical bond between Jews and Chinese restaurants, particularly at this time of year. The rabbi's advice? If you want a steady clientele, go kosher.

To get that status, Fong had to buy new cookware and dishes. "We had to open our kitchen to the rabbis," says Fong, a vegetarian and a Buddhist. "They checked everything."

That certificate is not the only evidence that Singapore takes seriously the "oy" in soy. A menorah is on display near Buddhist statues. On a wall are certificates that say a tree has been planted in Israel in honor of Fong and his restaurant. Latkes are on the menu.

But the most unlikely piece of Judaica is in the upstairs party room. Hanging in the back are two painted portraits - left in a house that one of Fong's waitresses bought - of boys in their bar mitzvah best.

The bar mitzvah boys are by themselves at 1 p.m. on Christmas, though the downstairs dining room is filling up. Among the first customers is a Jew, sort of.

"We're nonpracticing HinJews," says Elyse Fenton, sitting across the table from her Hindu husband, Peenesh Shah; his mother, Pina; and the married couple's wriggling 11-month-old baby, Mira.

A little later, the Fogels of Wynnewood arrive.

"Mike and the kids went to the synagogue [for Sabbath services] this morning," says Lisa Fogel, a physical therapist who visited a couple of patients Saturday before lunch. "We're going to have friends over later."

Eleven-year-old Emily Fogel feels good about how she spends Christmas, except for one thing this year.

"Today I wish, because Hanukkah was so long ago, that I got more presents," she says sheepishly.

Max and Sarah Gluck, brother and sister, are in from New York City visiting their parents in Center City.

Where else would a vegetarian Jew who keeps kosher go on Christmas, says Max Gluck. Besides, the food is good, and Fong "is so warm and inviting. He always remembers what I ordered. . . . He is a character."

As if on cue, Fong is standing beside their table.

"This is a very spicy Jewish boy," the owner deadpans.

Fong has picked up his clients' lingo. When he hears a diner mention a dumpling appetizer, Fong shouts out, "kreplach," the Yiddish word for dumplings. After the Fogels have paid for their meal, Fong says, "Todah rabah," Hebrew for thank you.

By 3 p.m., the mood is festive, and the kitchen is busy. Fong made the sauces in the morning, freeing up two cooks to handle the woks. They prepare dishes with names such as Drunken Treasure and Phoenix Nest as a woman makes dessert balls - a paste of sweet potatoes, cinnamon, and sticky rice rolled in sesame seeds.

Fong's wife, Ivy, and their sons, 23-year-old Chin and Ronny, 16, are serving.

"I just got back from Washington state to help," says Chin Fong, who is studying video-game art there. "I've worked every Christmas Day of my life."

Holidays like this at the restaurant are the only times the family is together anymore.

As the afternoon closes in on evening, the Fongs have little time to do anything but work. At 6 p.m., there will be a full house - even the party rooms upstairs. It won't be long before the bar mitzvah boys are alone no more.

Contact staff writer Carolyn Davis at 215-854-4214 or cdavis@phillynews.com.