BRANFORD, Conn. (AP) _ Work begins at 2 a.m. for the overseas operators at Lester Telemarketing Inc., about the time business executives in Bonn, Paris and Amsterdam start their workday.

A cacophony of foreign languages fills the crowded room, where some 15 operators at nondescript desks work the telephones in French, German, Japanese, Chinese and even Russian.

In an age when more and more companies rely on telemarketing to reach potential customers, Lester, based in this small community near New Haven, offers its clients something new: instant access to markets half a world away.

For instance, a publisher who mails out a computer magazine free to 20,000 computer engineers in 60 countries recently hired Lester to conduct market research.

The magazine had addresses for those receiving the publication, but wanted to know if it was being read both thoroughly and by decision-makers.

International Telefind, a subsidiary of Lester, dug up phone numbers for all those on the magazine's mailing list. Then Lester operators called them - in 30 different languages.

Since Lester began its foray into overseas telemarketing about a year ago, the operation has bloomed into a small but fast-growing part of the company's overall business.

While a number of American companies have telemarketing operations in Europe, often through a European affiliate, Lester is unusual in hiring native speakers to make calls overseas from the United States, said Joan Mullen, president of the American Telemarketing Association, a trade group.

The year-old venture comes amid a flurry of interest by U.S. companies in Europe's planned economic unification in 1992.

Moreover, phone calls from the United States have a certain cache for foreign business people, especially in countries where telemarketing is relatively new - and not yet annoying.

''I've been on the phone to a German company, and the chief executive will be in a top meeting. But the secretary will march right in and say, 'The USA is on the line,' and the CEO will stop what he is doing to talk to me,'' said Harold Robles, Telefind's director, himself fluent in English, French, German and his native Dutch.

Lester said its scores of telemarketing clients include Fortune 500 companies, publishing houses, major cable television companies, universities and charities.

In addition to its Branford, Conn., office, the company has branches in Dallas and Denver and recently opened a phone center in Toronto.

''The whole idea is to become a true single-entity international resource,'' said Robert Lester, the company's boyish-looking president.

Lester, 39, spent much of his childhood in Italy, where his father worked with the U.S. State Department. His bilingual upbringing shaped his business attitudes.

''I guess I was swept up by the shrinking nature of the world,'' he said. ''One day I just realized that everything is becoming international faster and faster and faster,'' Lester said. ''In 10 or 20 years, the company that has marketing abilities in many foreign countries with many foreign languages will have an extraordinary advantage.''

Lester's first challenge was to find well-educated, bilingual operators fluent in the languages of the dozens of countries he wanted to reach, from Europe and Asia to the Soviet Union.

He turned for help to the foreign language departments at nearby Yale University. He also resorted to flipping through the Yellow Pages, calling up Chinese and Japanese restaurants to ask the owners for help.

Another challenge was getting the telephone numbers of the overseas businesses his clients wanted to reach. In the United States, computer lists complete with phone numbers exist for almost everything.

Few such lists exist in other countries. So Lester established International Telefind to develop its own lists. Telefind employees spend hours on the phone with other countries' equivalent of directory assistance, trying to put together new lists for clients.

When a big project is under way, Lester is open 24 hours a day.