The expected presidential veto of the current U.S. trade bill is no balm for Asian exporters who fear the legislation in any form.

The underlying concern is that Congress will drop the contested plant- closing measure that irks Mr. Reagan, then resubmit the bill with all the other killer bee provisions.That could spark world recession, the South Korean government warned Thursday.

Protectionist elements in the bill have been a matter for our concern, said Foreign Ministry spokesman Kim Han-kyong in Seoul. The Korean government regrets that the U.S. Congress passed the bill as it stands.

In a toughly worded statement, the ministry said a revamped bill might undermine the long-continued efforts of the international community for harmonious and balanced expansion of world trade.

It sharply criticized provisions that would make retaliation mandatory in certain circumstances, saying this may hamper efforts by South Korea to push through its own trade-liberalization program.

Singapore officials condemned the bill as a major impediment to resolving U.S. differences with trading partners in Asia and the Pacific.

What has given the trade quarrel an added bitterness is the feeling on the part of the countries affected, said a Singapore official who asked The Journal of Commerce for anonymity.

They have close links with the U.S. (and) feel they have been deserted, just as the U.S. ditched Vietnam in its final hours. This is not being fair to friends of the United States, he said.

Another official attacked U.S. politicians as shortsighted when they conceive measures such as the Gephardt amendment, which would have taken the U.S. and the world away from an open international trading system.

Business leaders in Asia contend that U.S. trade problems can't be solved overnight.

The solution requires further efforts to reduce trade barriers on the part of East Asian countries, but also concrete measures by the U.S. to regain its competitive edge, one manufacturer said.

In Taipei - where tough trade talks are in progress with a U.S. delegation - a senior Taiwan official said a trade bill would have a serious effect on Taiwan's economic development because about 40 percent of Taiwan's exports are shipped to the United States.

Wang Chien-shien, chief trade negotiator, urged President Reagan to veto the present bill, and, by implication, any revised version.

In an apparent conciliatory gesture, Hsu Chao-lin of the Board of Foreign Trade pledged that Taiwan will continue with its trade liberalization to avoid being subject to retaliation under some punitive measure.

Japan's chief government spokesman, Keizo Obuchi, said the bill, which imposes sanctions against a unit of Toshiba Corp., may hinder world economic development.

The government of Japan strongly hopes that such a bill will not finally be enacted, said Mr. Obuchi.

A provision in the bill specifically sanctions a unit of Toshiba Corp. for selling sensitive military products to the Soviet Union.

Japan's Minister of International Trade and Industry Hajime Tamura said although the sanctions were regrettable, he is heartened to know a presidential veto can be sustained.