3 weeks in Thailand with a 3 year old was not one of my ideal holiday plans but it worked far better than I could have hoped for. I've posted the flight bits on the long haul thread so I thought I'd put a few other bits here.
For those who haven't seen my other comments on other threads, we had to travel for a family wedding so felt having made the effort to go so far we may as well extend the holiday as much as possible.
My biggest concerns were for dd's health, I've usually had a dodgy tummy in Asia so was worried for her. No problem, ham sandwiches were her staple diet (despite all the Thai green curry & satay she ate before she left she wouldn't touch it there..)
Travelling with a blonde, blue eyed toddler opened doors we didn't even know existed on previous trips - it became embarassing when the 70+ man and the heavily pregnant woman both insisted I took their seats on the BKK skytrain so dd could have a seat - apparently it wouldn't happen for a local child.
Dd got a bit phased when everyone (and I mean everyone) she met in the streets wanted to pat her head/stroke her/hold her hand/talk to her.

We would have had no problems if we wanted babysitters, but we felt more comfortable with her having a nap at the hottest part of the day then staying up to eat with us in the evening - but family helped out occasionally so we could talk as a couple.

I would definitely go back, I would NEVER have thought of going there with such a small child under normal circumstances but I'm glad we did. Dd did so many things from seeing amazing wildlife to sitting on an elephants knee and participating in an amazing Bhuddist wedding service that I really think she'll never forget it and to help that we collected loads of memorabilia to make a scrapbook.

Rhubarb, I've not put the detail of what we did here but if you want to know more ask Tech for my email address. Don't give up hope, you really can have a good holiday/tour with a little person, we travelled to 3 different places during our trip (and we shared a room with her for 3 weeks and still managed !) Sure it's not quite what it would be as a couple but it was so, so much better than I'd feared. We definitely did not reduce everything down to her level and were able to enjoy 'us' time too.