What is this?

I'm a bit crap when it comes to wildlife especially insects, so I would be interested to hear from anyone who knows what type of insect this is. My Khmer friends told me it was poisonous and they should know, though they then jokingly attempted to flick it in my direction. It was resting on a tree stump in Kien Svay, near Phnom Penh. It was a strange and intriguing looking insect with dazzling colours and a large proboscis, and I would appreciate more information, if you have it. Thanks in advance.