For me, the concept of health spas has always been associated with strictly-controlled eating plans and endless aerobic exercises. But, after being cajoled by a friend living in Thailand, I finally gave in. The promise was that it would be a thoroughly enjoyable experience that I would remember forever. "All you have to do is lie down and relax," she vowed.

So, on a humid Saturday afternoon I found myself discussing my "treatment package" with a therapist at the Oasis Spa in Chiang Mai, the wonderful walled city in the north of Thailand . The centre was set in a beautiful garden - a true oasis from the bustling street outside. As my friend and I had agreed to share a treatment pavilion, we tiptoed across a little stream and entered our pavilion - a teak building, fitted out with two massage tables. A glass wall looked out on a spectacular walled garden, which had a herbal steam room, outdoor shower and a spacious bath.

The programme I had chosen comprised the body scrub, the milky bath, an aromatherapy body massage and a hot herbal compress on my stomach and back. The full session, which cost about 70 US dollars, took just less than three hours. I started off with grave misgivings of how to behave correctly. What was spa etiquette? Did I have to undress fully? Do I wear a towel in the steam room? But my friend's advice was spot-on: "If you are unsure, just ask. No-one really minds what you do. Their main aim is to make you feel comfortable."

And they did. In the privacy of the pavilion, I didn't even feel the need for the soft cotton robe provided. The therapists are seemingly invisible. As for the treatment, I could actually feel the tension leaving my body. At one stage, smooth heated stones were stroked across my body and placed to rest on my stomach and back. I have no idea why, but it seemed to add to the feeling of total peace I experienced.

My favourite part of the treatment was the milk bath. My friend and I lay facing each other in the steaming hot outdoor tub, laughing and chattering away. But later we rested our heads on the edge of the bath and watching the clouds in the sky above. All too soon the three hours were over. My overall verdict is that the afternoon was, as promised, memorable. Nothing had prepared me for the incredible feeling of well-being after being stroked and pampered for a whole afternoon.

I chose Chiang Mai for my virgin spa experience as it is truly the "home" of the Thai spa industry. It has also become a centre for investigating the use and health benefits of plants and herbs in spas. Among the natural spa ingredients I have encountered are jasmine, oats, hibiscus, frangipani, pandanus leaf, betel leaf, coconut, turmeric, cinnamon and, of course, coffee beans.

The latest figures show that the country's spas attract more than three million visitors each year. And it's growing. A recent survey found that spa visits had increased by 64 percent in only three years and a surprising four out of ten spa visitors were male. As the industry grows, so do the treatments on offer. The latest innovation to hit the market will be a Tibetan-Chinese treatment centre set to open at Bangkok 's plush Shangri-La Hotel. These days few luxury hotels can afford to be without a health spa.

Chiva Som, which means "haven of life", is set on the beachfront of the Thai royal resort town in a seven acre tropical garden. The Chiva-Som philosophy is to combine ancient eastern therapies with the latest western techniques. As a world leader, it attracts its fair share of international celebrities who hide out in its very private suites.

The Banyan Tree Spa has the advantage of being set on beautiful Phuket island, where it forms part of the exclusive Laguna resort complex. The crystal-clear Andaman Sea is on your doorstep and it boasts a golf course, lagoon and swimming pools for you to while away the days. And the accommodation is unbeatable - in private Thai-style villas, some with their own swimming pools and jacuzzis situated in enclosed gardens. Some of the treatments offered here are Thai honey facials, Indonesian massage, seed facials, mud body masks, oriental foot massage and jet lag treatment. But many visitors opt for the one or two-day packages.

At the beach resorts you can get a massage for as little as 5 US dollars for an hour. Then there are the "massage shops", which specialise in foot massage and oil body massages for 6 or 7 US dollars. The smarter ones will cost around 20 US dollars. The spas that grace glossy tourist brochures and keep the visitors streaming in are the island spas. Phuket, Koh Samui, Phi Phi and Lanta islands all boast seaside spas that you will have dreamt of. Outdoor massage pavilions have the most stunning views of the ocean and surrounding islands - hard to match anywhere in the world.