Like many of of its neighboring Southeast Asian nations, Thailand is a country on the move - perhaps not as rapidly as Taiwan or South Korea, but buoyant nonetheless.

Since 1960, average real growth in Thailand has been a heady 7.6 percent. A major industrial sector has sprung up around this metropolis of 4 million.

There is still a depressing total of 11 million or 25 percent of Thai population, mostly in remote rural areas - who remain in absolute poverty. But that percentage is going down. In 1960, it was about 55 percent.

In terms of gross national product per capita, average annual Thai income works out to about the equivalent of $410, or about triple that of India.

And the World Bank - rated by others as the biggest single external influence on this economy apart from Japan - thinks there is every prospect that in 20 to 30 years, Thai per capita income could run a startling $1,500 or $1,600 - which would be roughly where countries like Iran, Yugoslavia or Portugal are today.

That may be a bit on the optimistic side. But the essential point is that the Thais have generated a fast-growing economy, including agriculture, largely by encouraging the private sector. Some 25 percent of GNP since the mid-1960s has been cranked into investment.

A very important factor in the Thai economic picture is an intelligent approach to birth control that World Bank mission head Hendrik van der Heiden says "appeals to the Thai sense of the funny and the frugal."

The Thais shun a direct monetary payment for the farmer who gets a vasectomy "as was the case in the disastrous, involuntary program tried by former prime minister Indira Gandhi in India). Instead, the cows of the Thai farmer who has had a vasectomy get the lifetime services of what is amusingly called "the family-planned bull."

This has worked so well that Thailand may be the one country where vasectomies are constrained not by demand but by the supply of money available for the government subsidy to the doctors. There are some good-natured titters - but that's all - when the "familyplanning bull" shows up.

Coupled with other forms of birth control, including the controversial Depo-Provera injection, which has been used here for years, the population growth rate has dropped from 3.2 percent annually in the 1960s to 2.5 percent and the Thais think it [WORD ILLEGIBLE] able to predict that it will dip to [WORD ILLEGIBLE] percent in 1985.

REDUCTION OF population growth rates will greatly help Thailand in the future, but there are still many major economic problems. The main feature of agricultural growth has been a big expansion of the land area in the north, where production is low.

These areas are subject to frequent flooding. But eventually, there will be no more room for agricultural expansion, and farm output will have to grow by application of increasingly modern methods. This is being helped along by extension work both in the World Bank and an Israeli consulting firm under contract to the Thai government.

The Thais are just beginning to develop export-oriented industry, some years behind Korea, Taiwan, and Hong Kong. The World Bank is trying to steer the government into producing capital equipment and engineering goods, instead of big steel mills of paper plants.

One imponderable is just how fast the Thais want to push economic growth. A sophisticated outsider thinks that in contrast to the Korean and Taiwanese, "the Thais do not look on growth as an objective in an of itself.

"They may continue at 7, 8 or 9 percent a year - all the elements making that possible are here. But they have a real queasiness about whether they want to grow much faster." Within the government, there is strong pressure for equity as well as growth - that is, a concentration or part of the effort on a redistribution of income.

THE AMERICAN ROLE and influence here is much subdued with the military out. Uban in the north is now a sleepy little town instead of the military outpost from which American pilots bombed North Vietnam.

Japan is now the big power here, as in all of Southeast Asia. There are only a few major American enterprises - a $100 million Esso refinery is the biggest, although plans are now underway by Union Oil and Texla Pacific for natural gas projects in the Gulf of Thailand.

The way some observers see it, the U.S. needs to meet the challenge of its growing trade deficit with Japan by challenging Tokyo with electronics, communications, engineering and other exports in Japan's own Southeast Asian backyard. The Thais who don't like the Japanese anyway, would probably help such an American initiative along. But American companies have been slow to see the opportunities in Thailand.