I burst into bitter tears the evening we arrive, a day of eating raw food behind me. I want a hot shower, a pina colada at sunset and white-linen sheets to snooze under -- a blissful week of indulgence. But the bathroom door is jammed open to the menacing jungle, a toad hopping by is eyeing me as I douse myself in cold water and I won't be eating solid food for the next seven days.
My man is to blame. A seven-day fast and detoxification programme -- all the rage in the Gulf of Thailand - will make an offbeat holiday, he says. I've relented and so we're here at the Sanctuary, a back-to-nature resort on glorious Ko Pha Ngan.
At least he too is now having second thoughts about how great it might be to discover a lost marble from childhood buried in his colon. For this is what we are here for: a week of twice-daily colonic irrigation sessions to help detoxify our bodies after 30 years of not-always pure living.
Best to eat raw foods for a few days beforehand, explains Moon, the radiant Wellness Centre manager who is his own best advertisement. But after just one day of crunchy vegies we've passed a pH test to show our bodies are up to enduring the battle ahead.
Day one dawns. Moon escorts us to one of the colonic rooms and explains how a baffling array of tubes, olive oil, toilet paper, hoses and a very, very big bucket of organic coffee swaying above us will work.
Unlike many similar setups in the west, sessions here are unsupervised. The first is awkward, but the waft of incense and the soothing strains of Norah Jones help to calm the feeling that this may be the wackiest thing since float tanks.
The second session is easier and from then on they're almost enjoyable. Discussing progress with the other half-dozen fasters around our bowls of vegetable broth each evening becomes de rigeuer.
Most awful however is swallowing down the dozens of herbal capsules and the four daily "shakes": a blend of psyllium husk, clay and watermelon juice that turns to pink glue if not downed within a few seconds. The psyllium explodes to forty times its size to keep stomachs full, and indeed for the first three days I'm too stuffed to think of eating.
The clay helps extract toxins from the system and is swept along by the psyllium, while the watermelon juice is just whoever designed this programme being a little bit nice.
Wonderful and sometimes mythical tales of fasters' experiences abound: missing childhood toys recovered, underlying diseases brought to the surface and cured and flashbacks for those who have lived lives on the fringe.
Nothing so exciting has happened to me by day four - although the caffeine-withdrawal headaches have faded. If anything, I am a dazed wreck: I have to rest at each of the seats scattered along the interminable route back from the centre to our bungalow, I nearly black out at the twice-daily yoga sessions and I forget what I am saying in the middle of sentences.
But I'm reading up on nutrition in the small library and discovering that what I learned at school is now way, way out of date. Theories of what makes a long-life giving diet abound and can leave a head in a better state than mine dumbfounded. But the ever-practical Moon has a simple mantra: "Listen to your body."
At least one positive becomes evident: my bikini isn't slicing through as much fat at the hips as it used to, I suddenly notice when having a splash at the beach.
On day six, I'm converted. I book in for a 90-minute Thai massage just to kill time. The masseuse, See, doesn't ask whether I have any problems. But I have been suffering from chronic pain down the right side of my body brought on by bad posture and too many hours sitting at a computer.
See's hands know anyway, helped along by the more sensitive and flexible state my body has now entered. When I sit up at the end of the session - interrupted only by a diligent staffer bringing me my unavoidable shake - I' m in tears. She has completely realigned my body.
On the final day I feel like I could keep doing this forever. I have irrepressible energy now and swim out to sea further than ever before.
Eating is like rediscovering food all over again. Even cucumber tastes delicious and the tiniest piece of garlic is an explosion of flavour. I can feel the direct link between what I put in my mouth and the energy that comes afterward.
I still lust for white linen sheets but have been amply rewarded for giving my body, instead of my senses, a real holiday.
For more information, please contact Moon at the Wellness Centre.
By Stuart McDonald
Last updated on 27th May, 2015.