Just how rich is Saudi Arabia? Not very, according to the kingdom's two top money managers.

Forget the tens of billions of dollars in cash and gold that this country holds abroad, they recently told a group of visiting Americans. Never mind an annual revenue surplus of at least $15 billion more. Leave aside the daily oil income of some $115 million in the country of only 7 million residents.

In the view of Mohammed Ali Abul Khail, the minister of finance and economy, and Abdel Aziz Quraishi, governor of the Saudi Arabian monetary agency or central bank, these are temporary and artificial surpluses that give a flasely sanguine picture of the kingdom's economic position.

"We don't have surplus, we have a temporary liquidity," Abul Khail said. He and Quraishi projected that Saudi Arabia's expenitures would catch up with its income by the end of this decade and that the reserves could be used by 1990, even allowing for increased oil production at ever-rising prices.

That may not be the view of Saudi Arabia held by the oil-importing countries that are going deeply into debt to meet their fuel bills or by impoverished Third World countries beseeching the Saudis for aid, or by the Western bankers concerned about the impact of Saudi investments on the world economic system.

There are foreigners here who dismiss this Saudi analysis as a rich boy pose. To them, Saudi Arabia, with known oil reserves of about 170 billion barrels and perhaps as much more still to be found, appears almost incredibly wealthy.

Saudi leaders do not see it that way. They say that this country is so vast and so underdeveloped, and its commitments so great, that it needs all the money it can raise - if not now, then soon.

According to Quraishi and Abul Khail, this country has only two resources, oil and cash, both depletable. Once extracted, the oil cannot be replaced. The cash from the oil is also being used up, by vast expenditures on modernization of the country and by inflation.

Quraishi said that because of Saudi Arabia's size, bigger than Western Europe, and the primitive backwardenss that still prevails in much of it, the Saudis do not have the luxury of putting their money in long-term, revenue-producing investments, such as real estate, as Kuwait does.

"This is a developing country and needs every cent," he said. The money is mostly kept in short-term notes and in liquid assets, he added, "so we can have it when we need it" to pay for the roads, communications, schools, hospitals, ports, factories, and water desalting plants that are being built.

He said the Saudis generally stay out of real estate investment and have a policy of never acquiring more than 5 per cent of the shares of any corporation outside Saudi Arabia. The money is in corporate bonds, government agency bonds and treasury notes, mostly in the United States, he said.

From figures given by Abul Khail and Quraishi, from the monetary agency's annual report, and from independent sources, this picture emerges of Saudi Arabia's cash position.

Reserve holdings abroad are about $26 billion to $28 billion, though total foreigh hodlings including non-liquid assets are estimated by some analysts at nearly $50 billion.

Oil revenues, which account for nearly all the kingdom's income, may reach $40 billion this year. Government spending will probably be no more than $25 billion, perhaps less in view of the government's program to reduce expenditures in an effort to hold down inflation.

According to Planning Minister Hisham Nazer, the country could cut its current oil production of about 10.3 million barrels a day in half and still have enough income to meet its obligations this year.

That may seem like a enviable position, but Nazer says that "to assume that Saudi Arabia is rich country is a big fallacy."

Finance Minister Abul Khail said, "Actual expenses are still less then revenues. But we are talking about the day the two curves meet." This, he and Quraishi said, would be before 1980.

They said this is because bills are beginning to come due for vast capital projects previously ordered, the costs of imported technology and services are rising, and the country's ability to spend is expanding as goods flow through new ports and roads.

"The costs of development are very high," Abul Khail said. "Oil production is increasing, but we believe the absorptive capacity is going up even faster. We can see the point where we will have to dip into the surplus."