Well, sir, all I can say that some ASD children are what I have heard the term used "runners." I believe in the ASD child's mind that the world is just open to them and they see no limits. They have no sense of fear. Maybe checking into a GPS device for him would give you peace of mind. May want to check with Autism Speaks (they may have the name of some carriers). I have been in the presence of some autistic children who are "runners" and they are quick. Also, purchasing a security system for your home (I apologize if I am assuming that you own a home and not rent an apartment)--should he open the door you would know immediately. Best of luck.

running/wandering is very common for children with Autism. My daughter was a runner but did grow out of it. Something we did (though not a complete answer to safety) was to play Red Light/Green Light game. We would hold her hand and run on green light stop on Red, we did this everywhere & constantly especially in parking lots. Eventually she began stopping when we shouted Red Light. This is not a substitute for safety procedures but it did help.

Actually I'm surprised that ABA therapists don't have experience with this behavior. I have heard it is quite common and one of my boys was a perfect example of this. He started at about age 2. And it was a common problem for at least six years. He needed to be constantly watched to make sure he did not run off. Besides opening doors and running he was great at scaling six-foot fences in less than 3 seconds and taking off for the hills. Unfortunately the only solution is your child would need to be watched whenever he is awake. While at home one solution I had was to change the doorknob on the bedroom backwards so to be locked from the outside. Then to make sure I could keep an eye on the situation in the room, I cut the door two thirds of the way up to create a Dutch door. That way the bottom was locked and the top could be opened to see what was going on (i.e. tearing the bed apart, taking off clothes and diaper, peeling the paint off the walls, etc.) Believe me, your patience will be taxed.

Thank you all from the bottom of my heart from the responses. It is very helpful. He does that only at school. He does not do that at home or grocery. At grocery stores, he does it sometimes, but it become less by time. At school, he opened the door and he laugh when he sees somebody chasing him. I am a single parent. When he gets kicked from the school, it affect my job big time.

A simple door alarm is very inexpensive. I think they have them at Home Depot but here is one on Amazon.
http://www.amazon.com/gp/aw/d/B008NXFKLK?cache=...(Phone number can only be seen by the question and answer creators)&sr=8-6

I wonder if you bought one and offered to install it (they just mount with double-sided tape) if it would help give everyone a little more peace of mind. It's obviously not a guarantee but if they hear the alarm when the door is opened perhaps it would help?