Lowell Thomas came back to Tibet yesterday, 28 years after he left on a litter with a broken hip.

The 85-year-old broadcaster and world traveler overrode the objecttions of Chinese doctors and officials in order to show his bride, Marianna, 49. "The Heavenly kingdom" of the exiled Dalai Lama, now ruled by Communist cadres from Peking.

Thomas and his traveling companions were greeted by two Chinese officials and one Tibetan when their plane landed after a three-hour flight from Chengtu. Thomas came off the plane wearing a Kazakhstan wool hat: a fur-lined Tibetan coat, its bright wool patterns made of natural animal dyes, and a flashy jeweled belt buckle from Alta, Utah.

The Communist officials posed happily with Thomas, making no reference to his past relationship with the exiled Buddhist leader or his prominent role in worldwide efforts for Tibetan relief.

Thursday, in Chengtu, Chinese doctors and officials tried to persuade Thomas that he should not risk his health in the 12,800 foot altitude of Lhasa. He insisted he was a mountaineer "going home" to the altitude he likes best.

They bowed to his wishes, when he and George Bush, the former head of the U.S. liaison office in Peking and organizer of the trip, agreed to take personal responsibility for anything that might happen in Tibet.

Thomas told his traveling companions that the last time he came here it was on the back of pack animals, across the Himalayas. At the gate to Lhasa, no longer standing, a delegation of Tibetan nobles, in colorful costume, rode out on tall mules, and laid silk scarves across his hands in a gesture of welcome.

This time, it was a motorcade of Chinese sedans that came out to the airstrip, 50 miles northwest of here, to meet Thomas and his traveling companions, who include Dean Burch, former Federal Communications Commission chairman and James E. Baker III, the chairman of the 1976 Ford presidential campaign.

As the party droce down a rough, twisting dirt road, past primitive mud and stone huts. Thomas and the others occasionally breathed oxygen from canvas bags placed in the back of the cars.

Thomas wears a pacemaker for a slightly irregular heartbeat, but he showed no signs of distress. Arriving at a guest house, Thomas gestured at the Potala, the mountain top palace of the Dalai Lama, and said, "Except for that, I would not know I was in Lama.

The old city Thomas knew is obsecured by the factories, compounds and apartments built by the Chinese since they put down a rebellion by the Tibetans in 1959 and exiled the Dali alama.

Today most of the people on the street were Han Chinese, wearing the green uniforms of the Peoples Liberation Army or the blue uniforms of the Worker Brigades. "This was the most colorful city in the world," Thomas said. "The people loved to dress themselves in fantastic coats and caps, and their horses were magnificently caparisoned. Every night, there was a parade of monks and nobles, with bright banners. They loved the color."

Lhasa was anything but drab today. Under a sky of incredibly pure blue and the surrounding snow-topped mountains. Chinese flags, billboards and posters heralded today's celebration of China's national day.

As he headed for a map, Thomas said. "I'm glad to be here and to see what they do. But I doubt it can match those pageants the Dalai Lama stages."

For years, Thomas appeared on the lecture platform as "the last man to leave Tibet." His journey out, in 1949, two years before the Chinese annexed Tibet, was marked by a fall from his horse, a broken hip, and a 17-day journey on a litter to safety in India.

He was not the first American to return. That honor went to a party led here a year ago by the man who is not President Carter's secretary of energy, James Schlesinger, who was then a private citizen. This is the first group of Americans since then.