My wife and I are planning a trip to Southeast Asia in Jan. of 2007 and thought it would be fun to take a bicycle tour while in the region. We have never toured before and so would definitely want a fully supported tour. I have found several companies online that offer tours (e.g. spiceroads, veloasia, skedaddle), but would like to hear of any first hand recommendations for tours and companies. We are completely open to the country/countries, though Thailand, Cambodia, and Malaysia are the most intriguing.
Given my wife's and my abilities, what would be ideal is a 7-10 tour that averages ~50 miles per day over flat to rolling terrain. We've driven over the Hai Van pass in Viet Nam a couple of times -- not something that we would want to attack by bike at this junction (maybe in the future... : ) ). Also, we aren't looking for luxury accomodations, but would prefer not to stay in completely decrepit guesthouses.
I went on a tour of Vietnam with veloasia back in 1994 and enjoyed it very much. This was back when Vietnam was an exotic place and there was not the internet and all of the information that is now available on the internet. With that in mind I could no longer imagine using a tour company to do a tour as it is just too expensive and very unnecessary, as all the countries that you mention have a bunch of information on them and are all very easy to tour around.
Take a look at www.crazyguyonabike.com they have many journals that cover SEA that can provide you with lots of good ideas. My personal favorite is NE Thailand, the scenery isn't fantastic but everything else is, roads-people-food-hotels-prices. Its pretty easy riding also as it's mostly flat. I've done rides there in January and the weather is very pleasant also. The only negative is that the rice has already been harvested so things look sort of brown and not as pretty as in Novemeber.
We thought that we were being a bit audacious doing our first bicycle tour in SEAsia, let alone doing an unsupported tour! I'd love to do so, since it parallels how we normally travel, but it probably is biting off a little too much at first. Hopefully after we get a few more miles under our belts...