Switching off is not as easy as it sounds. Monkeys are screeching, branches are rustling and invisible frogs are croaking in the vertiginous swirl of trees that surround me — but at least there’s no mobile-phone reception.

I’m at the Jungle Yoga retreat, buried deep in the world’s oldest evergreen rainforest, in southern Thailand. Encircled by towering limestone cliffs, it consists of a necklace of bamboo huts floating on the still waters of a lake. Few places can be more remote: with no running water, phone lines or electricity, daily life revolves around sunrise kayaking, yoga classes, jungle trekking, bathing in the lake and nocturnal stargazing.

The biggest challenge for me, though, isn’t touching my toes or balancing on my head for three hours. It’s learning to switch off, and my first lesson came on the long journey to get here. At nine that morning, I was standing on Don Sak pier clutching a tatty scrap of paper, with a raspberry smoothie stain on one side and scrawled directions on the other.

The handwriting belonged to the wild-haired Danny Paradise, a yoga teacher I’d met only days earlier, on Koh Samui. With an impressive roll call of students that includes Sting, Madonna and Paul Simon, Danny was inspiring, and I found myself agreeing to swap the palm-fringed island for what he insisted was “the most beautiful place on the planet”.

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Just as all yogic thoughts of peace and harmony were beginning to desert me, Sucheep, the retreat owner, appeared at the pier with his truck and a smile as bright as his red checked shirt. But the wait had been just the start.

It took a meandering four-hour drive, a long-tail boat ride, a half-hour jungle trek and a 10-minute bob on a raft to reach Jungle Yoga — which gave me plenty of time to ponder my lack of foresight in bringing kilos of gadgets when a healthy dose of patience and a yoga mat would have sufficed.

Surrounded by rainforest, the retreat is as basic as the setting is enchanting: washing takes place in the lake using biodegradable products, while toilets (flushed using buckets of water) are located on the lake shore, accessed by wobbly bridge.

The atmosphere is warm and homely — stacks of books, swinging hammocks — but my late arrival means a quick change in my hut and a dash to the yoga shala, a floating bamboo platform, where I join the first class.

My fear of being surrounded by people taking yoga very, very seriously swiftly evaporates, thanks to Danny’s infectious cocktail of wry humour and pearls of wisdom. At one point, after demonstrating an extraordinary tangle of a balance with legs flung over shoulders, he says calmly: “This position may be impossible now. But in many, many years’ time, if you practise every day, it will eventually become only very difficult.”

By the time class ends, the sun is behind the cliffs, the jungle chorus is reaching fever pitch — and it’s bath time. Jumping into the still, cool waters of the lake as stars rise in the sky, I become acquainted with the tricky art of washing my hair while treading water in the dark.

Later, at a long communal table laden with vegetables, rice and noodles, I discover a rainbow cross-section of people from around the world. There is Lida, a smiling air hostess from the Czech Republic, Don, a bearded lecturer from Canada, and high-maintenance Megan, a peroxide blonde New Yorker.

Later, as some of us lie on cushions on the floating deck, surveying a dizzying star-lit sky, an ear-splitting hyena-like screech suddenly emanates from the darkness. Not, it transpires, a nocturnal creature: but Megan’s reaction at spotting a frog in her hut.

Nights are early here, mornings serene, kayaking through low mist hanging in swirls above calligraphic tree stumps. Yoga takes centre stage in the afternoon, while the most memorable evenings take place when dinner is laid out like a picnic on a floating bamboo platform. The hours pass in a pleasant haze of stargazing, as fiery home-brewed spirit is passed round and Danny sings with his guitar.

When it’s finally time to swap this dream for reality, the jungle has already worked its magic: everyone, even Megan, seems more relaxed. Lugging my rucksack on board the raft and waving goodbye to Danny, I vow to return. But next time, I’ll pack lighter.

Travel details: Jungle Yoga (jungleyoga.com; prices depend on which course you book) holds retreats between November and April. Danny Paradise (dannyparadise.com) is next there from January 30 to February 10, 2010. The nearest airport is Surat Thani, from where the lodge will arrange transfers. Thai Airways (0870 606 0911, www.thaiair.com) flies there from Heathrow via Bangkok for about £550; book direct or through Opodo (0871 277 0090, opodo.co.uk).

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