LAS VEGAS, Nev. (AP) _ More than 10,000 visitors from 21 foreign countries are in town this week for the annual Comdex computer show as global visitors vie for an ever-growing share of the multibillion-dollar computer industry.

Hundreds of the 1,600 exhibitors at the show are foreign-based, each with an eye on a larger share of computer software and hardware marketed through some 100,000 dealers, distributors and manufacturers in attendance here.

''We've been getting hundreds of inquiries at our booth daily,'' said Anthony Wong, a representative for the Hong Kong Trade Development Council. ''We're expecting a record year for exports, with a 30 percent increase so far in 1987.''

The Singapore Trade Development Board also has a booth at this year's show, promoting the products of 15 companies headquartered in that Asian country.

''I'm very encouraged with the reception we're getting,'' said Lee-Pheng Wong, director of the Los Angeles office of the Singapore board. ''A lot of people didn't know us. This show is giving us a chance to show what we can do. Singapore has always been known for its quality. Now we're getting that message across to others.''

The foreign interest in the Las Vegas show is witnessed by the fact that several hundred of the 1,600 media representatives attending this year's show are from outside the United States. The show, which began Monday, ends Friday.

''We've been certified by the U.S. Department of Commerce as an international trade show,'' said Sheldon Adelson, chairman of the Needham, Mass.-based Interface Group, the Comdex producer. ''Our show is only one of 15 certified (by the federal agency) out of more than 10,000 trade shows this year.''

One of the benefits of the certification is that the federal agency helps match buyers and sellers at the show's international business center.

There is strong interest in Comdex around the world because it's the event where new products and technologies are introduced to a worldwide market, according to David Kaminer, a public relations representative. Products introduced at Comdex surface on the European market six months later, he said.

Special seminars during the week have been designed to familiarize foreign visitors with the ins and outs of importing U.S. products, and to teach U.S. vendors more about marketing their products abroad.