Nutrition and the Food of Thailand : Health: In a new book, a nutrition consultant investigates such ethnic cuisines as Thai, Indian and Chinese food, as well as contemporary American foods, salad bars and the menus of fast-food outlets.

Nutrition advice generally deals with commonly available foods, and there may be few guidelines for diners who deviate from the mainstream.

How, for example, would you evaluate such dishes as tod mun, tom kha gai, pla koong and tom yum koong? The first step is to find out what they are (all are popular Thai dishes) and then assess their nutritional merits.

For an explanation and analysis of these and many other foods, turn to “The Restaurant Companion,” a survey of 14 restaurant cuisines by Hope S. Warshaw, a registered dietitian and nutrition consultant (Surrey Books: $9.95).

Warshaw, a Bostonian, has investigated such ethnic cuisines as Thai, Indian and Chinese along with contemporary American foods, salad bars and the menus of fast food outlets.

She is enthusiastic about Thai food as a source of healthful meals. “I’m beginning to like it better than Chinese food, which I was practically brought up on,” she said in a telephone interview. “I think you get into heavier sauces and fried food with Chinese. It’s a little easier to steer clear (of these) in Thai restaurants.” Thai egg rolls, she said, “tend to be smaller, the soups are extremely light and there is not as much accent on beef and pork.”

The problem lies with coconut milk, which is used in some curries, soups and other dishes. Coconut milk is “relatively lethal,” said Warshaw.

According to USDA nutrient data, one cup of canned coconut milk contains 445 calories; about 97% of these are from fat and 88% of that fat is saturated, she said.

The calorie count for “raw” coconut milk, meaning that produced by squeezing the liquid from grated fresh coconut combined with water, rises to 552 calories per cup; 93% of these calories are derived from fat and 89% of that fat is saturated. Frozen coconut milk contains about 486 calories per cup; 92% of them are from fat and 89% of the fat is saturated. Although coconut milk is high in fat, “there is zero cholesterol because the product is not of animal origin,” Warshaw said.

As she points out, however, one usually eats only a portion of a coconut milk-based dish along with other foods, and this mitigates the harm.

For a healthful Thai meal, Warshaw suggests starting with a light salad or soup. “They are really nice fillers,” she said. A wise step would be to incorporate a number of vegetable dishes into the meal along with, perhaps, a chicken dish. “You don’t need as much protein as we tend to eat,” she said.

The dietitian starts each section of her guide with a passage on healthier eating out as related to the cuisine under discussion.

“Thai food, generally speaking, fits into the healthy goals for eating--light on the fats, meats and sauces and heavy on the vegetables, noodles and rice,” she writes. “Though there are some Thai foods and preparation methods one should avoid, there are many, many palate-pleasing entries on Thai menus.”

The importance Thais place on rice keeps carbohydrates high. The combining of meats with vegetables and the inclusion of vegetarian dishes on Thai menus makes it possible to limit protein from animal sources. “It’s much easier to eat less than four to five ounces of protein in a Thai restaurant than it is in an American steak house or hamburger joint,” Warshaw comments.

To guide diners on the spot, she has devised an easy-to-follow format that starts with lists of green- and red-flag words. Green-flag words that indicate acceptable dishes on Thai menus include “barbecued,” “charbroiled,” “marinated,” “lime sauce,” “basil leaves” and “bed of mixed vegetables.” Red-flag, or cautionary, words include “fried,” “crispy,” “until golden brown,” “topped with peanuts” and “made with coconut milk.”

Next, Warshaw gives a typical restaurant menu with check marks in front of preferred choices and an explanation of each dish:

* Tod mun, which doesn’t rate a check, is an appetizer of fried minced fish and shrimp cakes.

* Tom kha gai, another no-check item, is a chicken soup made with coconut milk.

* Tom yum koong, or shrimp soup flavored with lemon grass, chili paste, lime juice and straw mushrooms, qualifies for a check.

* Pla koong, which is spicy shrimp salad, also merits a check.

Warshaw presents model meals following such guidelines as low calorie/low fat; low calorie/low cholesterol; higher calorie/low fat, and low sodium. And finally, she defines spices, seasonings and ingredients used in Thai cuisine.

The large number of Thai and other ethnic restaurants in Los Angeles makes Warshaw’s guide especially helpful here. The book also covers Mexican, Italian, Japanese, Middle Eastern and French/Continental foods; gives pointers on ordering lunch, breakfast and brunch, and tells how to get healthful meals on an airplane.

“The Restaurant Companion” can be purchased in bookstores or ordered by sending $11.95, which includes postage and handling, to Surrey Books, 101 E. Erie, Suite 900T, Chicago, Ill. 60611.