Back in Chiang Mai. Chris and I returned from Doi Inthanon, where we had spent three days trekking, last night. This is easily the highlight of the trip so far, and our group of six trekkers, including Chris and myself and our guide, approached it with just the right mix of intellectual curiosity and a sense of humour.

We did plenty of trekking, of course, along with less strenous activities such as swimming under a waterfall in a lake in the mountains and playing Thai drinking games around the campfire. But it was the hill tribe people who really stood out. On the first night, when we stayed at an isolated lodge in the jungle, we were joined around our campfire by a deaf and dumb man who lived in a village in the forest and who is teaching himself to read and write English (he can read and write Thai) by asking passing trekkers to write words down for him in an exercise book. I taught him a little, of course, although I think I learned much more from him. On the second night, we slept in a village of the Karen, the most populous of Thailand's hill tribes, which was the poorest place I have ever been. It has no water and no electricity; corrugated iron roofs are a luxury, and most houses are built of wood and bamboo and rooved with leaves; and its people, refugees from Burma, are effectively stateless and exist totally outside Thai society.

Coming back to Chiang Mai after three days in the countryside was something of a culture shock, and its blatant commercialism and number of Western backpackers per head of population offend my sense of adventure as much as its pollution offends my lungs and throat. Still, it's not all bad. This afternoon we took a songthaew (a pick-up truck with seats, which are used as buses here) to Doi Suthep, a mediaeval temple on a hilltop above Chiang Mai, an island of serenity floating above the clouds of pollution which almost hid the city below. On the way up, we met Nick, a British photographer based in Kathmandu, who gave us some invaluable advice on trekking in the Nepali Himalaya and on the security situation in Nepal.

This evening we visited Wat Suan Dok, a monastery on the outskirts of Chiang Mai, where the monks regularly give visitors an insight into Buddhism in exchange for a chance to practise their English. Many of them speak it excellently, including Prawat, a Lao monk who in all seriousness invited me to travel back to his village on the banks of the Mekong in Laos with him when he returns in April. It was with deep regret that I had decline his offer.

Chris and I don't know where we are going next. We have four more days in the north of Thailand before we have to head south to meet Rachel in Bangkok. More news from somewhere, very soon.