Buddhists believe we are all reincarnated but that enlightened lamas can choose which body to return in. What makes this energetic child running around the grounds of a Kathmandu monastery unique is that he is the first American boy to be acknowledged in Buddhist circles as a reincarnated lama.

Sonam Wangdu was born in the same city, Seattle, to a devout buddhist but all-American mother, Carolyn Lama, and a Tibetan father, Tenzin Chopel Lama, who died in a car crash in 1993.

Mrs Lama, so-called for no other reason than that her husband, like many Tibetans, was named Lama, knew even before her son was born that he would be special. One night she dreamed of rising in the air to the top of a sacred stupa (a religious monument) in the Kathmandu area and of being able to see a line of shining stupas stretching to infinity.

But it was shortly after the boy, now known as Trulku-la (pronounced Tu-ka-la and meaning one who has chosen to take rebirth) or Dezhung Rinpoche IV, was born that two of the highest lamas who had known Dezhung Rinpoche III recognised his reincarnation.

Dagchen Rinpoche, Mrs Lama's lama in Seattle, and Sakya Trizin, another leader of the Sakya branch of Tibetan Buddhism in India, recognised the infant through signs during meditation, their dreams and divination. The boy has met His Holiness the Dalai Lama twice and is accepted by him.

Four years since his birth, Trulku-la is now the head of the Tharlam Monastery in Kathmandu, which he or Dezhung Rinpoche III, depending on how you look at it, re-established in Nepal in the early 80s.

Dezhung Rinpoche III, a learned scholar, had moved to America in the 60s following the Chinese takeover of Tibet and taught at the University of Washington, later co-founding the Sakya Monastery in Seattle, of which Mrs Lama is a member. He said before his death he would return in the body of a boy in the Seattle area.

It has been a nine-year wait, but the monks at the Tharlam Monastery now have their much-loved teacher back; Dezhung Rinpoche III ordained and taught many of the 41 monks there.

Two years ago, Trulku-la was enthroned at the monastery in a 41/2-hour ceremony before a crowd of more than 4,000, but later went home to Seattle. Now he has returned to stay and Mrs Lama is preparing to leave him for good.

A statuesque former Olympic-class rower, Mrs Lama, 38, sits framed in the window of the room she currently shares with her son. She knows everyone's main concern is how can she leave him.

'One TV channel asked me that same question four times,' she smiles. 'If you really love someone the way parents love their children you want what is best for them, you really do.

'An education like this, an opportunity like this, is incredible. To have your son raised in a way that you so much believe in couldn't be better. It's worth the sacrifice that I have to make.' Mrs Lama knows she'll feel the wrench of being away from her son as much as any mother. 'Boy, it's going to hurt. I know that. I'm not hard, I'm a good mother. But not only do I believe in the Buddhism and the education part, but, you see everything, it's a very nice place for a little boy to grow up.

'I wouldn't leave my child in an environment where he wasn't safe, happy, comfortable, secure and loved. I feel from the point of view of someone who is not a Buddhist this situation is still acceptable. He will have all the creature comforts - there's even a bath with hot water.' And he eats meat.

While the alleys to the monastery are as dirty as any Kathmandu street, once inside the grounds the atmosphere is comfortable, if not a little stark.

And far from the bleak monastic cell one would expect of a lama's quarters, Trulku-la's bedroom in a dormitory block standing apart from the main section of the monastery is filled with the trappings of any four-year-old.

In the corner of the twin-bedded ground-floor room stands the shrine to youth, a video/TV. Fluffy toys perch precariously on a curtain rail, a box full of Lego stands in another corner, a rattan unit is filled with books and games.

Two Tibetan rugs cover the parquet floor, bright orange curtains hang in the large windows and the beds, Trulku-la's raised slightly higher than his mother's as is tradition, are covered in fluffy red blankets and patterned sheets.

His day starts at 8 am - the monks get up at around 5 am - and in the weeks since returning to Nepal last month, his time has been spent simply 'running around and playing like any other child'. There are a number of lay children living with their parents in the monastery and some of the monks are young enough to befriend.

Last week, his lessons began. Slowly but surely, he will be taught the Tibetan alphabet, and, as he develops, his education will extend to subjects ranging from algebra to astrology.

'It's almost like a renaissance education,' says Mrs Lama. 'It is well-rounded. It's not just Buddhist philosophy. There's mathematics, medicine, astrology, physics. He won't learn American history, but I don't think that's such a bad thing.

'You find out in a situation like this what is important to people. One guy will come and say, 'But he won't be able to play Little League,' or, 'He won't be able to take piano lessons.' You find out what each person is holding on to. That's what they see he won't have.' It's an understandable concern. You have to believe wholeheartedly in what you're doing to uproot a boy from the perceived comfort of his suburban American setting to leave him in the Himalayan kingdom of Nepal, the fourth poorest country in the world. But there's no doubt of Mrs Lama's convictions. She refers to her son and Dezhung Rinpoche III as one and the same person - 'him or he' - creating some confusion in speech, but it's impossible when first meeting Trulku-la not to look for some sign of reverence or piety.

Watching him bound into the room it comes as some disappointment that he doesn't float two inches above the ground. His father's genes have given him an exotic look, but that's where the romantic image ends.

He ignores me up until the point I hand him the traditional beige silk scarf offered to lamas and returns it as is customary by placing it over my head but with less ceremony than he later exhibits when going to the lavatory.

Perhaps I can't see the signs, but what makes this clearly intelligent mother, a care assistant in Seattle, so sure her boy is the reincarnation of an 81-year-old man? A little wishful thinking maybe? Unlike other reincarnated lamas, Trulku-la has not had to prove himself by recognising possessions from his past life. 'Because the two highest lamas in the Sakya tradition agreed this is Dezhung Rinpoche, he didn't have to do any tests,' says Mrs Lama.

'And there are other things, like the enthronement ceremony, which would have gone wrong if he wasn't Dezhung Rinpoche. He would have thrown a fit and they wouldn't have been able to continue or something like an earthquake or tornado would have stopped the ceremony. But it was perfect.

'There have been many incidents when people have recognised him [Dezhung Rinpoche III], but much of it has been very subtle. In Seattle, he [Dezhung Rinpoche III] had his own house where he lived for years. Now his grand-nephew has it. We went there for dinner and everyone waited. Trulku-la came in and went immediately and sat down in his own chair.' Hardly conclusive evidence, but what would non-believers take as gospel proof? Whatever his past or future, Trulku-la in the present is a four-year-old, who, while being aware of his past life because he has been told so, seems unaware of his exalted position.

After his education at the monastery, he will go to the Sakya College in India, but will later return to Kathmandu where he'll teach the monks.

His mother expects to visit him three or four times a year, bringing her family with her - she says she'll blindfold them up until they enter the monastery grounds. But Trulku-la is unlikely to return to the West for at least eight years.

While Mrs Lama, who says she 'lived in the woods' before finding Buddhism and now wears Tibetan dress, believes Trulku-la will gradually become aware of 'who he is', others might suggest you could take any child, put him in a monastery, tell him who he is and before long he'd believe it.

Mrs Lama answers the suggestion as realistically as she can. 'Quite simply, why would I want to bring him here if I did not truly believe he is who he is? My belief in lamas is not blind. It's been eight years of experience, study, understanding, of being with a lama, of asking questions.

'I have incredible respect and trust in the lamas, so I feel very open to their guidance. So in something as important as Trulku-la, I respect their guidance in what I should do.' Certainly, Mrs Lama is no dippy-hippy-chick, but a woman who clearly believes in living her religion. She understands separation. She has a 13-year-old son from her first marriage, who lives in Indiana with his father, and sees him regularly.

While she thinks that separation may have paved the way for making this one easier, she believes the suffering she will have to undergo is part of a necessary experience to purify her karma. Buddhists believe karma is the sum of a person's actions in previous lives; it is this which decides an individual's state in future existences. 'It was me, rather than Trulku-la who was actually chosen,' says Mrs Lama. 'I was chosen with my husband because Dezhung Rinpoche III knew I would give him up. I believe that's totally why.' One of the young monks, Ngawang Tankyong, 20, has been assigned as Trulku-la's attendant. He will move in to Mrs Lama's bed when she leaves and has already taken over some of her responsibilities like 'dressing him, brushing his teeth and giving him his vitamins'. Mrs Lama has no concerns at passing over her son to Ngawang's care. 'He's loving, kind, gentle, peaceful, enthusiastic. The monastery got together and said who would be best. It's in their interests to select the right person. Trulku-la is going to be their teacher.' Mrs Lama has no fears over the lack of female influence in his life, but can take comfort in the knowledge that a nun, Dezhung Rinpoche III's sister, lives in the room next door. She's a grandmotherly figure in her 70s, but if you believe in reincarnation, she's actually Trulku-la's sister.

Nor is she concerned at committing Trulku-la to a monastic life, and, by definition, a celibate one. 'Missing out on sex is not the worst thing in the world. I believe it will be made up for in the richness of his life. What you've never had, you never miss,' Mrs Lama says.

No one knows what the long-term future holds for him. If he turns to his mother aged 12 and says, 'Marm, what am I doing here?' Mrs Lama says he will be free to come home, but she doubts that will happen.

He will see his family three or four times a year, and his paternal grandparents, who live down the road, can pop in when they like. He will have had a constant friend and guardian sleeping by his side and an extended family of monks who adore him.

Throughout my interview, Trulku-la refused to answer my questions. But there was one that received an instant reply. 'What will you do when mummy leaves?' 'I'll cry,' he said. So will mummy.