Paced by its flagship, the Orchid Queen, what might have been called Nancy's Navy sailed into the heart of Bangkok today carrying Nancy Reagan to a lunch date with the prime minister of Thailand.

And what a way to go.

Her fleet was an assortment of two dozen police patrol boats, royal Thai gunboats and military frogmen in inflatable rowboats. As the Queen and her escort vessels smartly plied the Chao Phraya River, three military helicopters also kept watch from above.

The traditional river hubbub had come to a standstill, and along the shoreline were dozens of uniformed guards bearing rifles. Thai officials confirmed reluctantly that it was the most extensive security operation for any foreign VIP in recent memory.

The White House left nothing to chance, however. Besides an expanded complement of Secret Service agents, Mrs. Reagan was accompanied by both the head of her own detail, Tim McCarthy, and Secretld,10 Service Director John Simpson.

She was piped aboard her orchid-bedecked boat by a Boys' Club bamboo pipe band waiting at the royal pavilion opposite the Grand Palace, where she is staying.

Three days ago in Bali, when some young folk dancers performed for her, Mrs. Reagan attempted a little footwork of her own. Today she tried her hand at shaking the pipes. The good-natured reviews from the American news media contingent were mixed.

At the end of the two-mile boat ride waited Prime Minister Prem Tinsulanond, a soft-spoken, mild-mannered man who told her a little later that her visit to Thailand was "something special, something dearly wished.

"It also makes abundantly clear your conviction of the need for close international cooperation to combat the evil of narcotics," Prem continued before an audience that included Americans as well as Thais.

As chairman of Thailand's Narcotic Control Board, Prem said the government's approach to the problem is in "a total manner through both the suppression and prevention of drug abuse.

"The government itself takes seriously our duties in law enforcement," he said. "We believe it's worth the painful sacrifices and losses that have to be endured. Driving out opium warlords and tracking down traffickers, our men have not died in vain."

In her response, Mrs. Reagan praised the Thais' efforts, singling out the involvement of King Bhumibol and Queen Sirikit as having "a tremendous effect.

"When the government works to enforce the laws and stop the flow of drugs," she said, "when private organizations work to publicize the antidrug message, and when families work to keep their children safe and loved, the future is far brighter."

Earlier, the first lady toured the Temple of the Emerald Buddha, which is set amid the dazzling collection of golden spires and pavilions that make up the Grand Palace.

She took off her shoes to enter the temple, where the Emerald Buddha (in reality, carved from a solid piece of jade) sits atop a golden altar awaiting his next change of robes by the king. That will come sometime in July, when Bhumibol climbs a ladder to dress him in a golden diamond-studded tunic to keep him cool.

Today, though, the Buddha was wearing his gilded rainy season robe, and Mrs. Reagan, who has been changing her clothes three times a day even though her hairdresser, Julius Bengtsson, says she "loves the heat," was frankly impressed.

"Beautiful," she said of the Buddha. "It defies description." And of the complex in general, "I don't know what I did expect, but I didn't expect all this."

When Prince Subhadradis, an archeologist and historian, pointed out some giant figures, called yaks, and explained that they guarded entrances against evil forces, the first lady's antennae for the lore of superstition sprang into action.

"I'd like to take some of those things that are supposed to keep off the bad spirits with me," she said.

Tonight might have been a scene out of "Anna and the King of Siam" -- so like a Hollywood set was the dizzying spectacle of lighted buildings, spires, statues and sculpted plants making up the Grand Palace.

In fact, it was in Chakri Hall, built by King Mongkut's son, Prince Chulalongkorn, that King Bhumibol and Queen Sirikit's dinner for Mrs. Reagan was held.

Mongkut, the king depicted in the film -- which has been banned in Thailand -- never lived there, but his portrait hangs in the king's gallery. Mrs. Reagan and Queen Sirikit passed right by it when they walked to the audience room to join others in the royal family.

With them was a man reporters mistook for a Thai security agent because he carried a two-way radio. On closer inspection, he turned out to be the king, a very modern monarch when it comes to keeping in touch with his realm.

The queen wore a Thai silk gown of dark and light blue adorned only with three strands of pearls. Mrs. Reagan wore a silk chiffon gown with a yellow, red and lavender floral print. Her necklace appeared to be crystal, with matching earrings.

At the dinner, Mrs. Reagan sat between the king and queen. Also at the table were three of the royal children and two of their consorts, Prime Minister Prem and U.S. Ambassador William A. Brown. At another table was Thailand's ambassador to Washington, Kasem Kasemsri.

King Bhumibol and Queen Sirikit had no trouble at all finding where they were supposed to be sitting. As is the case for Britain's Queen Elizabeth II, theirs were the only places without place cards.

As an aide to Elizabeth once explained, "She knows where she sits."