South Korea has joined the world's exclusive club of advanced semiconductor producers. But for the time being, it almost would prefer that no one took notice.

This fall, it exported its first lots of a computer memory chip known as the 64K RAM, with more than 65,000 "random access" memory cells. Next year, a new factory being built south of Seoul will begin turning out its version of the most advanced commercial chip, the 256K RAM, with four times the memory in the same-sized sliver of silicon.

Armed with technology licensed from American Telephone & Telegraph Co. and other leading chip producers, South Korean companies are quietly mapping plans to invest close to $1 billion in new semiconductor plants with an eye to the world market that is now dominated by Japan and the United States.

It is a daring venture for an electronics industry as young as South Korea's. But the Koreans aren't blowing their horn for fear that they could provoke a protectionist response in the United States and other foreign markets.

The world's $20-billion-a-year semiconductor market, the Koreans know well, is one of the sensitive arenas of trade competition for the United States, watched closely by American politicians and corporate executives alike.

Stiff antidumping duties imposed this year by the United States on Korean color TVs are seen here as an example of what Washington will do when it feels threatened. The Koreans also are facing pressure to reduce their exports of steel to the United States.

Thus, many industry figures here prefer not to discuss chips at all with foreign journalists. Those executives who do so often dwell on Korea's lack of experience and tiny output -- well under 1 percent of the world's semiconductor capacity is here, they say. Some scoff at the suggestion of direct competition with the United States.

"Maybe five or 10 years from now," muses semiconductor specialist Lee Woo Seok of the Ministry of Trade and Industry.

Politics aside, there is no question that Seoul is taking an enormous risk. The worldwide industry operates boom or bust, drops models and factory technology almost overnight, and is facing oversupply and rock-bottom prices for many of its products.

Still, Seoul hopes to succeed by marrying foreign know-how and diligent, low-paid labor -- electronics workers here made about $1.20 an hour in 1982, only 11 percent of the average U.S. manufacturing wage that year, according to the Bureau of Labor Statistics. Korea's overall export drive, which will bring in almost $30 billion this year, has made tie-ins of foreign know-how and low-cost labor work time and again.

The deals are now on the rise in the electronics industry, which traditionally has skimped on research and development. According to the U.S. Embassy in Seoul, there were 33 technology import agreements in 1981, 60 in 1982 and 80 in 1983.

At worst, executives and officials here appear to believe, the semiconductor ventures will be a costly learning experience that will give South Korea a leg up for commercially viable production of future generations of the product.

The semiconductor industry here dates to the 1960s, when foreign companies began setting up shop to assemble imported parts. Today, 20 such ventures make a range of simple products such as watch chips and transistors. They control 80 percent of South Korea's $650 million a year in integrated-circuit exports.

South Korea shipped its first color TV set abroad in 1974. Today, electronics exports have mushroomed to $3 billion a year and include computers, telecommunications equipment and components.

As the industry grew, government planners began finding fault in foreign control of production of a component as crucial as the semiconductor. They encouraged domestic industrial groups to enter the business for themselves and go for advanced designs.

Led by Samsung Semiconductor & Telecommunications Co., the industry now plans to invest about $875 million in advanced products between 1983 and 1987, $270 million of it in 1984 alone, according to the U.S. Embassy here.

Samsung, part of a $7-billion-a-year trading and manufacturing conglomerate, bought a license for its 64K chip from Micron Technology of Idaho. Its dust-free factory near Suwon City south of Seoul turned out the first Korean chips this summer. The first exports went to two California companies in the fall.

It also bought rights to a Micron-developed 256K chip, a device that is starting to replace the 64K, and began building a production line in Suwon. It has finished a prototype chip and plans to rush it to market this spring or summer.

Samsung's plans call for 64K capacity of 27,000 four-inch wafers per month, and 20,000 six-inch wafers for the 256K chips.

Gold Star Semiconductors, part of another South Korean conglomerate, is also in the race. It is reported to be working on its own 64K and, according to press reports, a 256K version, also using licensed technology.

Gold Star has linked up with AT&T to produce so-called "thin-film hybrid" integrated circuits and with LSI Logic for chip design technology. Other major entrants are the Hyundai and Daewoo industrial groups and a smaller company, Korea Electronics.

Industry offices are clustered with the government-financed Korea Institute of Electronic Technology in Kumi town, already dubbed "the Korean Silicon Valley." Samsung and Hyundai, meanwhile, have set up subsidiaries in the real valley in California, with Gold Star putting money into a joint venture there.

Serious questions remain, however, about quality. While some Korean industry sources say Samsung has brought its 64K "yield," the percentage of chips leaving the assembly line in usable form, down to internationally competitive levels, others say the industry as a whole has not come to grips with quality.

Even if it is achieved, however, profits are not assured. Japanese and U.S. companies have ignored warnings of a glut and are continuing to build new factories, putting further downward pressure on prices.

A 64K chip sold for $10 in 1982, but this fall was fetching less than $2 at times. For the 256K type, U.S. wholesale prices plunged from $22 last summer to only about $12 last month and are forecast by some industry analysts to go down to $10.

Faced with facts like these, industrial analysts in Seoul are by no means united behind the projects. Earlier this year, the Korea Institute for Economics and Technology, another government think tank, warned against overinvestment, a problem that plagued the local petrochemical and heavy machinery industries in the late 1970s.

Other critics point out that Korean companies have little in-house development capability and could be left high and dry if foreign licenses dried up. Already, the Japanese are reluctant to part with technology, fearing it eventually will boomerang against them.

The caution camp includes Daewoo Semiconductor. Executive Managing Director Lee Hun Jai notes that the industry is "kind of a fashion show. Every season, the clothes style is changing." Settling on a product too quickly could mean getting saddled with a costly plant that makes something nobody wants.

Lee feels Korea can produce the 64K competitively, but the extensive automation required for more advanced versions such as the 256K may make them a bad bet. "We may not have any cost advantage with those types of products," he said. "We would have to buy the technology, and there is no advantage in the labor costs."

He suggests instead formation of cooperative ventures with foreign companies. The Korean partner would produce second-level components, leaving the top line to the foreign partner. "I don't want to compete with the advanced countries," he said.