The day after the Loy Kratong celebrations in Bangkok, Anna and I headed north, stopping at Ayutthaya then taking the night train up to Chiang Mai. From there, a short flight across the mountains brought us to Mae Hong Son, in the northwest of Thailand close to the Myanmar border. From the plane we looked down on the green hills and river valleys of this mountainous region, and could just make out some trails winding across the hillsides. For the next five days we would be walking along those trails, sleeping in villages and sampling many variants of the local rice wine. We had organised our trek over the internet from England (more accurately, Anna did most of the work while I was in Nepal), and the company we had chosen seemed responsible enough - but I still had a few doubts about the ethics of "hill-tribe trekking". It's one of the main tourist draws of northern Thailand, but brings with it the inevitable impact on local culture. I wasn't even sure if it was right for us to be there at all.

The "hill tribes" are not ethnically Thai, and do not really "belong" to any nation state - traditionally, they have moved around without concern for national borders. Some of them have inhabited the hills of Mae Hong Son province for many years, while others are more recent refugees from Myanmar, fleeing the oppressive policies of the military government. Many aspects of their way of life have remained unchanged for decades, even centuries. For example, the design of houses and the patterning on clothes have been handed down through generations, as have religious traditions and agricultural practices. Many of the communities practice slash-and-burn farming techniques, leaving square patches of cleared and cultivated land on the thickly forested hillsides.

At Mae Hong Son airport, our guides and porters were waiting for us when we got off the plane. They all preferred to be called by their nicknames, maybe because they were fed up with farangs' pathetic attempts to pronounce their real names. Our trek leader was called Ki, which means "small" in Thai (although he wasn't that short). As well as being the only English speaker in the team, he was also proficient in the languages of the Shan and Karen people, two of the largest ethnic groups in the area. The three porters, who would carry the food, bedding etc. were friends or relatives of Ki. The elder statesman of the three, the uncle of the youngest, was known as the Troll, possibly because of his weather-beaten face and stained teeth. He was rarely seen without a huge Camberwell Carrot of a self-rolled cigarette hanging from his lips, but the fumes he took into his lungs didn't seem to affect his fitness - even with a heavy sherpa-style basket on his back, he climbed up those hills just as fast as the rest of us.

On the first morning we rode in a 4WD along the dirt road out of Mae Hong Son, until it became impassable; then it was time to put on the backpacks and walk. Ki had worked out a route that took us through villages inhabited by Hmong, Lisu and Karen people, and because he knew some of the families in the villages we would be able to sleep in their houses. The first overnight stop was at the Hmong village of Ban Hua Ha, which we reached at about 5pm. The light was already fading as the sun dropped behing the hills - night comes early in the mountains - and people were walking home from the fields to their houses. Pigs and chickens were running around, excited that it was feeding time, and a few children laughed and looked excitedly at the two strangely-dressed farangs. Our host for the night was a jovial middle-aged man with a crippled leg, who walked by leaning heavily with both hands on a long wooden staff. He lived next door to his brother, who had two wives and an enormous number of children, and together with three or four other houses the buildings formed a rough square, with a courtyard in the centre from which a path led off to the communal washrooms. The houses were all of a similar design - large wooden buildings raised on stilts, with the living areas on the first floor and the space underneath used for storing farm equipment and a few animals. The kitchen was the only room at ground level - ours was a small hut with a mud floor, where our guides started cooking dinner over the smoky wood fire while we sat down to rest in the courtyard next to a few women doing embroidery, and watched the children playing a game with spinning tops.

Ki explained to us that the people here were not used to seeing foreigners, but their reactions towards us were friendly. The children were curious, and would stare at us, either with bewilderment or bursting out laughing, while some of the older people were more shy. The only hostile reactions were from the dogs. Half an hour after we arrived in the village they were still barking and howling, and wherever we walked one or two of them would follow us, growling menacingly. Going to the bathroom in the middle of the night was genuinely frightening; a dog lurked in every dark corner, and with their eyes glowing green in the light of our torches they looked like the hounds of hell on our tail. I am eternally grateful to the village kid who kicked two snarling dogs out of my path as I was returning from the washrooms to the house. After dinner we sampled the local home-produced Lao Khao, or rice wine - Ki also called it Rakxi, the same word I had heard in Nepal for a similar drink. It tastes a bit like sake, although the Hmong version was much stronger than the ones I'd tasted in Nepal. Rather disturbingly, it came not in a bottle but in a clear plastic bag, but it tasted good and gave a nice warming feeling as it went down. In a few days, we were to encounter a rather more potent version of this drink.

The dawn chorus started long before dawn, with a couple of roosters trying to out-crow each other. It was about 4am. Soon they were joined by the chickens, pigs, dogs, and just about anything that was capable of making a noise - I lay in bed for a couple more hours, but there was no chance of getting back to sleep. The dogs roaming around the courtyard had started to become accustomed to having us around, and so our trip to the bathroom that morning was a little less scary than the night before. However, as soon as we ventured farther and tried to have a look around the village, we found our paths blocked by even more bad-tempered dogs, to whom we were strangers. I felt very glad that I'd spent all that money on rabies shots back in England. One place we did manage to get to was the school; we were invited there by one of the teachers, who had joined us for dinner the night before, and had explained that although English is on the curriculum, it is very rare that the children have any contact with native English-speakers. The school had just one classroom which looked clean and well-maintained, and we walked into the morning's lesson where 25 or 30 children (about 9 or 10 years old) were learning basic arithmentic. They all stood up to greet us, and after learning a few of their names Anna managed to improvised a short English lesson. They were shy at first, but she soon got them talking - so if in 50 years time anthropologists discover a remote village in the Thai hills where the inhabitants all speak with a Swedish accent, we'll know why.

Ban Hua Ha was the most remote village we visited, and over the following days our living conditions in the villages got easier; it felt like we were gradually walking back towards civilisation. There were no more xenophobic dogs, just the ubiquitous roosters who seemed to take a malicious pleasure in waking us up in the small hours. I was developing a pathological hatred of roosters. Our second night was in the Lisu village of Doi Ma Phrik, where we were guests of a man who used the income from the occasional tourist group to supplement the money he made from growing and selling chillies. Through Ki, acting as interpreter, we learned that the man's wife had left him, taking their children with her, and that his chilli-growing enterprises were less than successful. His house was slightly away from the rest of the village, and I wondered if he had become some kind of outcast, or had gone into self-imposed exile.

Sometimes the walking was hard: for the whole morning of the third day we pushed our way along an overgrown path, which probably had not been used since the end of the rainy season. Thorny branches snagged our clothes, and long leaves with serrated edges slashed at any areas of exposed skin. We were back on more well-trodden routes by the afternoon, with maize and rice fields next to the road. Ki led us up to one of the fields, where we met the couple, friends of his, who owned the house where we would spend the night. At the corner of the field was a bamboo pole, about 2 metres high, with a small basket on the top. Our hosts explained that this was for making offerings of rice wine, corn cobs etc. to the spirit of the field. Just like in the hills of Nepal, religion in this region is a blend of Buddhism and traditional animistic beliefs in the spirits of rocks, streams and fields. When we reached the house in the village, I noticed that the Buddhist shrine in the upper room had a statuette of the king of Thailand where the Buddha image should have been.

Before starting out on the trek, I had feared that some or all of the villages would be little more than outdoor theme parks, where the local people crowd round groups of tourists and pester them to buy souvenirs. In fact, this never happened. Not once during the trek did a child ask for a pen, or sweets, or one Baht. None of them wore David Beckham or American wrestling t-shirts. No-one tried to sell us souvenirs. I think the reason was that we were doing a longer trek than the standard packages advertised by the guest houses in Chiang Mai and Mae Hong Son. These treks are usually for two or three days, but by taking five days we were able to walk farther out into the hills and avoid the crowds. The villages on our route get the occasional westerner passing through, but the real tourist boom has yet to arrive, and I can't help hoping that the situation stays this way. It's not that I'd like to stop all other tourists doing this route - I just hope that the number of tourists trekking through remote villages remains low enough that they do not have a detrimental impact on the culture. It's even possible that they could make a slight positive contribution, both in terms of cross-cultural understanding, and hard cash.

Our final overnight stop was at the house of Ki's father-in-law, who welcomed us by having a rooster killed and plucked for the cooking pot. (It was good to think that there would be one less of the little bastards contributing to next morning's wake-up call.) He was proud of his home-brewing skills, and showed us the large plastic bucket in the kitchen where he kept the fermenting rice mixture from which the Lao Khao is distilled. After dinner (rooster curry and rice), he presented us with two glasses of the stuff to round off our meal. Within a couple of minutes, the vapours rising from the glasses made the room smell like a paint factory, and as I swallowed the first sip it felt like my throat was suffering irreversible damage. Anna, who knows a thing or two about hard liquor, was interested in the distillation process. "How do you judge the temperature without a thermometer?" she asked. "Experience" he replied. After a short discussion about the boiling points of methanol and ethanol, we decided that it might be best not to drink any more.

The final day's walk saw us scrambling over boulders, wading through rivers, edging nervously along narrow ledges and trying not to think of the consequences of a misplaced foot or a loose rock. I carried a big stick to help me balance, which I'm sure saved my life a few times, and was relieved that when we arrived at the finishing point my only injury was a single leech bite. After saying goodbye to the Troll and the other porters, Ki and his friend rode us (and our heavy backpacks) to the airport on the backs of their motorbikes. Anna caught her flight back home, and I walked the couple of hundred metres into the town centre. I was in a strange mood as I sat in a bar by the lake that night, and I realised that for the first time on this trip I really was alone. Up to then, there had always been someone else around: the tour group in Nepal, Paul in Bangkok, Anna on the trek. Now it was just me, and every decision from now on would be up to me - the route, the things to see and do, everything. There was no safety net, nothing to stop me screwing the whole thing up if I wanted to. Even the decision of where to go next after Mae Hong Song seemed impossibly daunting. Too many possibilities! I've never been any good at making big decisions, so I started with an easy one: I ordered another beer.