BANGKOK -- If the crowds mobbing the 17th Annual International Bangkok Motor Show in April were any example, the Thais are going noisily car crazy.

And that's just for openers.

Vehicle sales here have almost tripled since 1989, reaching 571,580 units last year, more than 9 out of 10 of them assembled in the country. Today, Thailand is not only the world's second biggest market for pickup trucks (after the U.S.) but is fast becoming a major vehicle producer, the "Detroit of Southeast Asia."

"By the year 2000, Thailand will have an aggregate car production capacity of 1 million units per year," predicts Chakramol Pasukvanich, deputy secretary general of the Board of Investment.

His country is coming of age automotively in quick time. Until five years ago, Thailand imposed some of the world's highest tariffs and taxes on motor vehicles, banned imports of completely built-up units (CBUs) and limited domestic production. Then, in July 1991, the government reversed course, slashing duties and taxes, permitting CBU imports and encouraging local production.

Today, 12 companies are assembling trucks and cars here while several others are readying massive construction plans. Recent announcements include:

* General Motors Corp.'s Adam Opel AG subsidiary has picked Thailand for the site of its $750 million Asia Car plant. The plant will build an Opel Astra-based subcompact beginning in 1998, with capacity for 80,000 to 100,000 units a year.

* Toyota Motor Corp. will begin building a Tercel-based model and Corona and Corolla models when its new plant south of Bangkok opens in 1998. Camry output will be added to the mix in 1999.

* Ford Motor Co. and Mazda Motor Corp. will jointly produce 100,000 pickup trucks a year at a greenfield plant beginning in 1998.

This interest is understandable when you look at Thailand's past, present and future. The Thai economy has been growing more than 8% annually for over 10 years.

"Chances of maintaining this growth rate through the turn of the century are very good," says a foreign economist in Bangkok.

Per-capita income has more than tripled in the last 10 years to $2,800, and an affluent middle class is emerging, centered in Bangkok.

Thailand's economic foundations have changed significantly in recent decades. Agriculture, predominant in the 1980s, now accounts for only 11% of Gross Domestic Product (GDP) while industry's share has jumped to 30%.

Half of the 4.4 million vehicles in operation are over 10 years old and there is still only one motor vehicle per 15.5 people here compared with 1:5.7 in Taiwan and 1:2.2 in South Korea.

Producing vehicles here is relatively easy and inexpensive. Thai workers, loyal and quick learners, earn one-tenth Japanese wages. A parts and components supplier base numbering more than 300 producers is expanding while their capability broadens and quality improves, with engine and transmission parts still the main imports. And although local supplier output is still low, costs are reportedly 25% to 75% lower than those in the U.S.

Perhaps one of the most encouraging signs is that the country is becoming politically stable. That's despite 18 coup d'etats since Thailand became a constitutional monarchy in 1932. The military is now in retreat. And while the leaders of 11 civilian political parties constantly reshuffle power in coalition governments, a cadre of capable bureaucrats actually runs the country and is keeping it steadily on course.

"There's no chip on Thai shoulders. They want to be the regional leader and create a real free trade area here," explains a diplomat in Bangkok.

The Japanese were the first foreign investors to sense the Thai potential, investing almost $10 billion in the late 1980s.

"The Japanese are famous for coming into a country, investing in manufacturing and creating demand for their products," says Tim Dunne, Director of Market Research for Auto Resources Asia.

"Japanese investment is the foundation of Thai prosperity," adds Shigeki Higashi, an economist with the Institute of Developing Economies in Tokyo.

Firm numbers are hard to pin down, but new investment each year, much of it foreign, is now estimated to be an astonishing 40% of GDP. The Japanese are still in the lead with an estimated $14 billion in place, followed by the U.S. with around $12 billion.

Much of the Japanese money has been poured into the automotive sector where the vehicle of choice for almost two out of three Thai buyers is a pickup truck.

No automaker has full-scale production facilities in Thailand, and key components such as engine and transmission parts are customarily imported. The regulations call for local content of at least 54% for cars and 62% for trucks but, to meet World Trade Organization rules, these requirements must be abolished by the year 2000.

Toyota and Isuzu Motors Ltd. are the market leaders with Nissan Motor Co. Ltd., Mitsubishi Motors Corp., Mazda and Honda Motor Co. Ltd. in hot pursuit. Together, these six producers captured 85% of all Thai truck and car sales in 1995 and all are carefully positioning themselves to stay on top.

* Toyota recently opened a new plant 60 miles (100 km) southeast of Bangkok to build cars including the new AFC (Affordable Family Car), a Tercel-derivative designed for the Asian market. Camry output will be added in 1999.

"The car share of our sales will gradually increase to 40% or 50%, but the Thai market is unpredictable, and we don't know when," says Suphot Visudhiphol, director of sales and marketing.

* Isuzu, long the pickup sales leader and innovator in Thailand, slipped to second place behind Toyota in 1995. But plans are to expand capacity of the current plant.

* Siam Nissan, struggling to overcome recent setbacks, has recovered somewhat from plunging car sales in 1994 and still plans to raise car and truck capacity from around 100,000 currently to 140,000 in 1998.

* Mitsubishi has transfered all pickup production here from Japan. "The 1-ton pickup is Thailand's national car," says Susumu Nakagawa, executive vice president of MMC Sittipol, a joint venture in which the Japanese company has a 48% stake.

Capacity is now 190,000 units per year -- 114,000 pickups, 60,000 cars and 16,200 large trucks -- more than enough to meet export and domestic demand.

* Mazda currently is squeezing nearly 24,000 trucks, cars and buses out of an elderly plant originally designed to produce 6,000, while eagerly awaiting the AutoAlliance start-up.

This Ford-Mazda joint venture will invest $472 million in a greenfield site 75 miles (120 km) southeast of Bangkok where pickups should begin rolling off the line in May 1998. At full production, the plant will turn out 100,000 CBU and 35,000 CKD units -- and there's room to expand. "We see the car market expanding and intend to add a second product," says Executive Vice President David Snyder, explaining that "a critical mass is building in Thailand, and if you want to compete here you have to assemble here."

* Bookings for the 1.3L City sedan, Honda's new "Asia car," were three times higher than expected, and the 1996 forecast of 45,000 City, Civic and Accord sales may have to be revised upward.

The City will be made in Indonesia, Malaysia and the Philippines as well, with extensive regional production-sharing, including Indonesian cylinder blocks, Malaysian bumpers and instrument panels, Philippine manifolds and exhaust converters, Chinese camshafts, and Japanese engine and transmission parts.

The U.S. presence in Thailand still is modest.

Chrysler Corp. began assembling right-hand-drive (RHD) Jeep Cherokees here last September and launched imported RHD Grand Cherokees and RHD Neons this year, but volume still is tiny, maybe reaching 7,000 units in 1996. But "We're looking to expand our presence in Thailand," says Bill Klingler, Chrysler's director of Southeast Asia operations.

Thailand is one candidate for a new $130 million assembly plant Chrysler is considering building in the region.

GM will open its $750 million Opel Astra assembly plant south of Bangkok in 1998 to supply mostly regional markets. GM says the plant will employ 2,000 workers at full production and include body and paint shops. GM chose Thailand over the Philippines for the new plant.

"GM is coming into Asia late and with all guns blazing," says Mr. Dunne, a native Detroiter who foresees a bad case of overkill: "The Thai car market is still very small, only 163,000 car sales in 1995 including over 25,000 imports. One U.S. assembly plant could easily handle it."

Cars are gaining in popularity, especially in Bangkok, and both Toyota and Honda obviously aim to satisfy this expanding demand and hedge against any change in Bangkok policy.

CBU car sales last year totalled 54,819, up almost 2.5 times from 1992, despite duties and taxes ranging from 137.2% to 257.7%, which raise prices to astonishing levels. Chrysler's Grand Cherokee sells for 2,090,000 baht ($83,600) while the Neon fetches 775,000 baht ($31,000.)

So far, the Thai government still favors pickup production, exempting them from excise taxes that range from 32.5% to 45% on cars, depending on engine size. As a result, small trucks sell for roughly half the price of cars.

The biggest sales growth in the next few years -- 10% annually according to some experts -- will probably be registered by pickups and take place in the countryside where these multi-purpose vehicles best fit people's needs.

Despite impressive gains, plenty of problems remain for Thai leaders and foreign automakers here.

Basic infrastructure badly needs improvement, especially in the provinces and in the transport sector. Congestion has become so severe in Bangkok that residents have begun muttering about committing "trafficide."

There is increasing discontent with Japanese companies unwilling to create a more self-sufficient Thai automotive industry. A Board of Investment report notes with succinct understatement that "Technology transfer has been slow, at best."

The shortage of engineers has become chronic. Yet educational standards remain low, with only six years mandatory schooling at a time when technology requires more skilled workers -- and wages here are higher than in neighboring countries.

Although the Thai people are traditionally non-confrontational and tolerant, social inequalities threaten social unrest.

For example, an estimated 40% of GDP is concentrated in Bangkok, home to only 10% of Thailand's 60 million people, and the income gap -- an estimated $7,800 per capita in Bangkok, 10 times that in the countryside -- is widening.

On the automotive front, the critical question now is how much is too much?

"There are too many assemblers and too much excess capacity even when exports are factored in," says Bunzo Suzuki, managing director of Sukosol and Mazda Co.

Exports, although negligible so far, are expected to expand as Thailand strengthens its position as a regional hub.

As a vehicle producer, Thailand has no regional rivals.

Near-term at least, its main focus will be on expanding domestic sales, which are expected to reach 800,000 or more by the year 2000, probably six out of 10 of them pickup trucks.

And at least in the foreseeable future, Japanese producers are unlikely to lose their lead -- or their edge.