Kubulan Los, son of a converted Lutheran lay preacher, usually eats a sandwich at his desk for lunch. Then, if there is time, he takes a nap on his office sofa. Sometimes his children call him at work to remind him to bring home enough cash so they can go to Roy Rogers for dinner.

Whenever he goes to the White House, which has been three times in the last two years, he rents his tuxedo. He rarely goes to cocktail parties and wherever he goes, he is constantly explaining to people where he comes from -- not the kind of thing ambassadorial egos thrive on.

As top emissary to Washington from Papua-New Guinea, a tiny country in the south Pacific known to most Americans as the site of fierce battles in World War II, Los heads one of 144 foreign missions in this city's diplomatic community. Living in Washington for many of the 6,400 foreigners who work in these missions is "a dream come true," as Los' secretary put it. But more often than not, their lives here bear little resemblance to the glamorous image of diplomatic life in Washington, one of cocktail parties in chandeliered rooms, chummy tennis games with influential people and chauffeured drives to "crisis" meetings.

As a look behind the scenes at the Embassy of Papua-New Guinea shows, diplomatic life can be routine in its chores, modest in its life style and almost anonymous in its existence.

"Well, we've been discovered," joked Los when a reporter arrived and asked to see how his embassy worked. In two years in Washington, the ambassador, a former secretary of transport and justice in his own country, had never been interviewed.

He represents a rugged country about 100 miles north of Australia where jungle-covered mountains and swamps kept some of its 3 million people of Melanesian stock from making contact with outsiders until the 1930s. This is the country where Margaret Mead researched her anthropological milestone, "Growing Up in New Guinea" and the adventurous heir Michael Rockefeller met an untimely death. The people speak over 700 languages and their lingua franca is pidgin English. Two weeks ago, the country voted for a new prime minister, its second election since independence from Australia in 1975.

There are no guards or policemen outside the corner suite of six rented rooms on the fifth floor of an office building at 1140 19th St. Only a foot-square bronze plaque emblazoned with Papua-New Guinea's national emblem, the bird of paradise, and the words "Embassy of Papua-New Guinea" gives a clue to what is there. Pasted next to the plaque is a handlettered sign: "Office hours 9-12 and 1-4."

Behind the door, Los works with a staff of three other Papua-New Guineans, including a secretary who at the age of 20 was given the choice of working in London or Washington and an affable consular official who works out his frustrations at lunchtime playing video games. Two Filipinos, receptionist Lita Ferrer and chauffeur Severino T. Salang, were hired locally.

Ferrer sits at the reception desk in the small foyer that, except for the absence of Muzak, a rack of pamphlets on Papua-New Guinea and two traditional cloth designs on the wall, seems like any American waiting room. In contrast to most embassies where presidential (or dictatorial) visages stare down from walls, there is not one picture of Papua-New Guinea's leadership hanging in the embassy, a fact that reflects the relaxed attitude that Papua-New Guineans have toward their officials, rather than any political disaffection.

"I was excited about coming to Washington because I had heard so much about it," said Los, a mild-mannered man who laughs easily and by all accounts runs one of the most efficient embassies of a developing country in Washington.

"The first time here is really amazing, getting to know my colleagues and the official people. There are so many diplomats and you have to hunt to get what you want." This is the 42-year-old ambassador's first foreign posting.

Two tiny flags of the U.S. and Papua-New Guinea stand on of Los' uncluttered brown formica desktop. A huge map of the world is pinned to one wall. A small portable radio rests on a side table. A tie rack with two spare ties is clipped to the edge of the bookcase, on which sits a small copper bust of Abraham Lincoln and a framed color photograph of Los (in his rented tuxedo) shaking hands with President and Mrs. Reagan at the White House.

"Because the embassy is so small I get involved in some things that in a bigger embassy, where the ambassador is more like a public relations man for his country, the ambassador would not be involved in," Los said. "I get involved in financial details which I didn't expect. We have no press officer, no cultural officer or information officer or defense attache."

One recent day Los, who is a lawyer, was poring over Papua-New Guinea's tax laws to answer a question about lump-sum payments in the case of nationalization. Another day found him taking notes at a panel discussion on the Law of the Sea at Baltimore's Convention Center. In larger embassies, both tasks would have been done by junior officers.

Taking its cue from the ambassador's personality, the atmosphere at the embassy is informal and friendly. Salang, who drives the ambassador's black Lincoln Continental -- one of Los's few concessions to diplomatic pomp -- does not wear a uniform because "the ambassador is not so strict on that; he's a very simple man."

There is little hustle and bustle, something Los takes with equanimity. Remarking on one recent appointmentless day in his office, Los told a visitor she could "watch nothing being done."

Those working on the same floor as the embassy say they never see much activity there. "It seems kind of dead over there," one remarked.

Early each morning in a back room of the embassy a telex machine begins chattering with a dispatch from the Department of Foreign Affairs and Trade back in Port Moresby, capital of Papua-New Guinea (which is 15 hours ahead of Washington time). In many embassies this room is equipped with sophisticated communications equipment and, in some cases, electronic spying gadgetry. But in this embassy there is just a simple telex, a photocopying machine and a small refrigerator. No codes, no bugging equipment. "We're not that important," Los said.

The daily telex dispatch contains a news summary of Papua-New Guinea's three newspapers and, on some days, instructions for Los, who also telephones his government about every two weeks for discussions.

If there is an urgent matter to discuss with the U.S. government, Los calls the Papua-New Guinea desk officer at the State Department to arrange a meeting. Occasionally, he meets with the deputy assistant secretary of state for East Asian and Pacific affairs.

Both sides say relations between the United States and Papua-New Guinea are good. The only major dispute between the countries centers on tuna. Disagreement over who owns the tuna in the sea caused the only "crisis" in bilateral relations since Los came here, he said.

That happened about six months ago when Papua-New Guinea seized a U.S.-registered tuna boat and charged it with fishing without a licence in its waters. The United States, which says that all tuna outside a three-mile coastal area of any country is fair game, protested. The conflict was resolved diplomatically -- most of the discussions took place in Port Moresby -- and "it didn't reach the level where the two governments had to seriously talk," said Los.

The embassy also has regular contacts with the Peace Corps, which now has 16 people working in Papua-New Guinea, and the World Bank, where two times a year Los signs a loan agreement negotiated by a team of Papua-New Guinean officials who come to Washington for that purpose.

Los, who is also his country's ambassador to the United Nations, says he has little contact with other diplomats here and when he does it is usually to lunch with representatives from other Pacific Ocean neighbors like Samoa and Fiji.

For small embassies like Papua-New Guinea's, budgetary restraints put a limit on the kind of entertainment the ambassador can do. When Los and his wife, Hilan, entertain at their rented, split-level home just off MacArthur Boulevard in Northwest Washington it is usually an informal gathering that includes Americans who have been to their country or officials visiting from home. They have no domestic help and Hilan spends her day caring for their four children, three of whom attend Francis Scott Key public school.

The country they represent is little known to Americans and "those who know of it have this exotic image of it as one of the last places on earth to be mapped out, sort of like Shangri-La," according to Ed Geibel, the Peace Corps desk officer for Papua-New Guinea. So Los' public relations task goes far beyond just polishing the image of his country here.

"Basically, an explanation of where we come from and where our country is, it's almost a daily job. I suppose it does get monotonous," Los said.

"We try to explain that it is in the Pacific and north of Australia but sometimes they don't even know where Australia is," Hilan said.

This ignorance is not two-way. "I would pray to the Lord, the first time I leave my country to go abroad, it must be to America," said Los's secretary, Winnie Ugava. "My next choice was Honolulu. So when I found out that my flight here stopped in Honolulu, it was like dream come true."

But some of her girlfriends, perhaps envious, didn't approve. "They said I should stay home to be near my parents. In a country like Papua-New Guinea, mothers don't let their daughters go too far. But my parents were all for it," said Ugava whose shoulder-length black hair is gathered in a pony tail at the back of her neck.

The road that brought her to the tiny room across the hall from the ambassador where she takes his calls, writes his letters and transcribes tapes of conferences he attends, began when she applied for a secretarial job in Papua-New Guinea's foreign affairs department. "Fifty-two girls applied for the jobs, only 12 were chosen, but only two of us showed up for work," said Ugava, who took a one-year secretarial course after high school in Port Moresby.

"After a few months I was called in and told I could have a choice of two cities, London or Washington, and which would I prefer," said Ugava. "I said, 'Can I come back with the decision ?' I didn't know that much about either of them. I asked diplomats who had traveled abroad and all of them suggested I should get Washington; securitywise they said it would be good. But I don't know what they meant by that."

Her smile temporarily fades into a look of dismay when asked if she thinks she might be bored back at home at the end of her two-year tour. "I think so, I'm going to have to go through a cultural readjustment," said Ugava, who called American men "very straightforward."

"I don't want to return but I have no choice." She will work in the foreign department again and has her "eyes on London or Brussels" for a future assignment.

Ugava lives in an apartment with a friend on New Mexico Avenue and is driven to work in the embassy's station wagon by the embassy's counselor, John Balagetuna, who in keeping with the embassy's informal style sometimes comes to work in a green striped pullover shirt. He is a short man with an oval face and next to his left eye is a faded circle tattooed into his skin, a common marking on both men and women in Papua-New Guinea.

Balagetuna's main job is to drum up investment in his country, but much of his time is spent answering inquiries from U.S. companies seeking to sell goods like baby food and shoes in Papua-New Guinea.

"It's time-consuming, you get bogged down with this routine stuff, so I spend less time in trade promotion," said Balagetuna, sitting at his desk on top of which is a file tray with shelves labeled 'Secretary' and 'Wait!'

Kila Ara Karo is the only aide who has previously worked abroad for his government, which has 10 diplomatic missions. He spent two years in New Zealand and three in Brussels.

"To clear my mind of certain things," Karo said, he likes to play video machines on his lunch hour in a restaurant downstairs. "I like to take vengeance on those robots, but unfortunately they always seem to win."

Karo, a tall, light-skinned man with a long Afro and wide smile, does the embassy's accounts. (It costs his government $390,000 a year to run its Washington mission, he said.) But his main job is giving out visas -- about 80 a month. Many go to businessmen. Some go to tourists, linguists, anthropologists and botanists, all drawn to his country, Karo says, "because they see it as the only country left unspoiled."

But the largest number of visas go (and this Karo himself finds strange) to missionaries.

"We have been open to missionaries for a long time, so I do not know why we need more of them. We even have our own theological seminary. Why do we have to import them? Practically everyone in the country has some affiliation with a Christian church. I don't understand why more missionaries have to go in. To convert whom? It baffles me.

"They used to come mostly from the big churches: Catholic, Lutheran, Anglican, Methodist," he said. "But now we get them from small churches like "The Church of God, One Way" and "The Four-Square Church." We joke about the names. Right now we have them mostly coming from California. It must be a famous Christian state."