I visited Thailand in May 2010... had to make a last minute change of plans to stay most of the time in Phuket (as the 'red shirts' vs Government protest was on in Bangkok. Thankfully (after the 'red shirts' were 'flushed out' - I still got to Bangkok (and saw my friends - from Netherlands, working there for a NGO- which was my original intention).
Both in Phuket and Bangkok I felt really quite safe. But then again, I'm a very well travelled person, having lived in other developing countries for many years. Be safe, keep 'carry-able' gear with you, and don't 'show off' or go to remote locations unless you're confident.
I took my 7D with 15-85mm on every outing, and depending on what I was going to see, either also took my UWA (10-20mm Sigma) or my Canon telezoom. I'd not hesitate to go there again with my gear, which includes a white Canon 70-300mm L. I would even swim in the sea, keeping an eye on my bag (but then again, it wasn't too busy at the beach - as it was off-peak season, so the beach wasn't crowded at all).
Pick pockets can be in every country, so just 'be wary'. Best wishes, and SE Asian has some spectacular scenary, colours, culture, etc.