S. Korean presidential campaign moves abroad - and into provinces. Ruling party's Roh heads to US, as opposition wrestles over which Kim to field as its candidate

Roh Tae Woo, leader of South Korea's ruling party, takes his campaign for the presidency to Washington and Tokyo this week, while his principal opponent, Kim Dae Jung, stumps selected cities and towns in this land of 40 million people. Mr. Roh, a retired general who is quiet in public but warm and astute in personal conversation, is scheduled to meet President Reagan in the White House today. Tomorrow, he will face the National Press Club in a performance designed to introduce him as a statesmanlike figure on the world stage.

Mr. Kim made an emotional visit to his home region, Cholla, last week, then tested his popularity in the neighboring region of Chunchon. He cannot have been displeased by a crowd estimated at 50,000 shouting ``Run, run, run!'' Saturday night in Taejon, capital of North Chunchon.

The opposition Reunification Democratic Party (RDP) has yet to decide whether to field Kim Dae Jung or co-leader Kim Young Sam as its candidate in the presidential election to be held in mid-December.

The former Kim is both charismatic and controversial, because of his allegedly left-leaning political and economic policies. Kim Young Sam, more conservative in both fields, is considered to be more acceptable to South Korea's silent but powerful military leaders.

``The two Kims have got to realize that they are, in fact, a coalition,'' said an influential member of the nonpartisan National Coalition for a Democratic Constitution (NCDC). To this member, the presidential campaign could focus on two opposing contentions:

The government's: the Korean people need strong leaders, otherwise they will fall apart.

The opposition's: the Korean people need democracy, not dictatorship; civilian rule, not military.

But if the opposition is to have a chance of winning against a well-organized government party, each Kim must be prepared to concede something to the other. Although Kim Dae Jung seems to be preparing an active campaign for the presidency, a number of observers including the NCDC member cited above believe that he does have a fallback position. That position is to let Kim Young Sam become the presidential candidate while he takes over the party presidency.

So far, Kim Young Sam seems to be resisting this proposal, but some think the resistance is one stage of a complex negotiating process going on between the two Kims. Both recognize, perhaps to a greater extent than their followers, that they need each other.

That being so, said the NCDC member mentioned above, the two Kims and their followers must work out a precise allocation of duties so that the RDP can maximize its strengths and minimize its weaknesses.

Each Kim still insists the party will field only one candidate. But in the popular sweepstakes, Kim Dae Jung has stolen a march on his rival by demonstrating, not only that he reigns supreme in his home region, but that he can win votes in other populous centers such as Taejon.

For 16 years, the military regime made Kim Dae Jung a nonperson. His picture never appeared in the news media. He was never allowed to make a public speech. And he was almost always under house arrest. Yet his fellow citizens of the two Chollas never forgot him.

His visit to his home district Sept. 8 to 10 was a triumph. Stops in Kwangju, Mokpo, and Haei Island were planned in meticulous detail. All the crowd control was done by Kim Dae Jung's own youth corps, the government police remaining discreetly in the background. Despite all the pre-trip rumors of sabotage either by leftist radicals or by clandestine government agents, the trip was completed without incident.

Kim Dae Jung's organizational skills are legendary, and if, in the end, it turns out that the other Kim becomes the candidate, these skills will be essential for an opposition win.

Meanwhile, Roh Tae Woo will stop in Tokyo after his Washington visit to meet Prime Minister Yasuhiro Nakasone and to address Japan's National Press Club. Korean-Japanese relations are a sensitive subject, and Roh's willingness to face a polite but critical audience shows his determination to be seen as not ducking any tough issues in his quest for the presidency.