This is still the queen of Southeast Asian capitals, in spite of the devastation caused by three years of Khmer Rouge rule. Along its wide boulevards the trees are now aflame with flowers.

Yet this beautiful city remains deserted. Thousands are camping on its outskirts but the new authorities in Cambodia will not allow them in. The city has been empty for three years. It has no food stocks and no markets or other places where people can buy rice, vegetables and other necessities.

Even if the government were to set up shops, there is no currency to spend, money having been abolished by the old regime.

There is no piped water supply. Corpses in the wells poison water. There are no schools or hospitals. Vietnamese engineers are putting up small generators to light up a few streets and houses. Plans are reportedly being made to install a big power unit to supply the whole city.

Another problem facing the new administration is identifying those who say they used to live in Phnom Penh. All those in the outskirts are dressed in peasants' black shirts and trousers, having been forced to work in the fields for the past three years. They were robbed of their identities three years ago when they were marched off to primitive agricultural communes.

At Sreng Chameri, a hamlet four miles from Phnom Penh where 4,543 people are waiting to go into the capital, I met a man in his 40s, dressed in black. Working in the sun has tanned him and malnutrition has caused white patches on his dark skin.

He says he is a doctor but he has no papers. Can the new government give him a hospital or dispensary to run?

Others say they were professors of mechanical engineering, or chemistry. The new government has, at the moment, no means of verifying these claims and giving them appropriate work.

The government has established offices at the outskirts to verify identities and issue papers so people can go into the capital and reoccupy their homes.

It is also trying to create jobs. The old Pepsi-Cola factory of the Sing-Thai company, owned by a runaway Chinese millionaire, has been reopened and 50 of its 300 workers have returned with their families. The problem now is how to sell the drinks when there is no currency. The state has been buying all the output and sending some of it to the provinces. There is a shortage of sugar and so the factory works fitfully.

The same is the case with the Chip Tong textile factory on the outskirts. The plant was reopened in February. Of its 800 workers, 200 have returned. Nobody knows where the others are. Those who have returned say some, including two skilled technicians, were killed. Under the pre-1970 government of Prince Norodom Sihanouk, it produced 20,000 yards of cloth a day. Now it is short of raw material.

The workers said that under the Khmer Rouge government of Premier Pol Pot, they worked without wages. They would start at 6 a.m. and work until 11 a.m. when they were given their first meal, a bowl of rice and salted fish. The evening meal at 6 p.m. was the same. They had meat once in two months, depending upon the supply. They said they were always hungry.

At both factories, the workers pleaded for foreign aid. Could the International Red Cross and other humanitarian organizations help with food, clothes and medicines?

Elementary medical services have been started by Vietnamese doctors. They are now taking in people who say they used to be doctors in the past. Yet one hardly notices this small activity in this city, which used to house 2 million.

Pochentong airport, Phnom Penh's main airfield, now receives three regular flights a week from Ho Chi Minh City (Saigon). Rows of Chinese-made artillery and antiaircraft guns, given to the ousted government, stand where they were unloaded from Chinese planes.

On the way to the city, we stopped at Pochentong pagoda. Its compound is full of weeds and littered with spent artillery shells. Belts of rifle bullets rust on its steps. Inside, there are piles of meteorological equipment, including weather balloons in packages, and boxes of artillery shells. Statutes of Buddha lie broken inside and outside-reminders of the defeated government's suppression of religion.

Along the avenues, in the former central market and in open spaces everywhere, coconut trees had been planted, crowding the flowering trees. The aim was to return Phnom Penh to the countryside. Between the new coconuts, more Chinese artillery was parked in rows.

Farther on stands the beautiful empty shell of the university complex, built by the Soviet Union in Sihanouk's days, its shutters ajar and paint peeling. We passed the technical faculty, the National Defense Ministry, the faculty of arts, the railway station, and the faculty of medicine, all empty. Next, the ruins of a church.

Finally, we arrived at the old Hotel Royale, which has changed its name many times recently. The government that deposed Sihanouk renamed it Hotel Phnom. Under Pol Pot it was called the State Guest House. Now it has no name.

There was no piped water, and washing was done in the old swimming pool at the back with the help of a basin. The water was now dull green. The next day, girls brought buckets of water to my room.

For food, there was rice, a few shreds of cabbage and a tough, dried-up piece of chicken, all brought from Vietnam.

Before leaving we went to the National Bank. Pol Pot's men had placed explosive charges and blown it up before they left. The streets around it were littered with brand new currency notes. They included currency printed by the Lon Nol government (1970-75) in Munich, and a few notes printed by the Pol Pot leadership, before it abolished money.

Iron grills of shops in front of the new market had been broken open, and the goods inside were not looted but destroyed. One must have been a large optical shop. People had trampled over cardboard cases of spectacles and lenses, and only the thickest of the lenses had survived.

In other shops were broken and damaged tape recorders, hi-fi equipment, sewing machines and other expensive goods.

As fighting against the Pol Pot forces goes on in the west of the country, the new government is raising its first army division, under the command of Khang Sarin, the commander of the capital garrison. In the open spaces outside his headquarters, recruits are being trained. Soon the division is to take over security duties in Phnom Penh from the Vietnamese. CAPTION: Picture, Thousands of former residents have been denied permission to reenter the city, and the streets remain bare.AP