"The following was sent to me from the USA, I dont know if it applies in other countrie
Subject: What to do if your cell gets stolen
To check your Mobile phone's serial number, key in the following digits on your phone: * # 0 6 # A 15 digit code will appear on the screen. This number is unique to your handset. Write it down and keep it somewhere safe.
Should your phone get stolen, you can phone your service provider and give them this code. They will then be able to block your handset so even if the thief changes the Sim Card your phone will be totally useless.
You probably won't get your phone back, but at least you know that whoever stole it can't use it either. If everybody did this, there would be no point in stealing mobile phones." KO
Has anyone experience of blocking a phone in Thailand?