For South East Asia, I am not sure how much a Pacsafe will help you in protecting your equipment and keeping it safe. Outright bag snatching or theft is what usually occurs, rather than someone slitting a backpack open (although that's not to deny the latter can happen too). Generally, South East Asia is a safe place and your things don't get stolen. You need specific situational awareness, such as the fact that there are motorbike-based bag snatching gangs in Phnom Penh or that when travelling by bus in Thailand, some unscrupulous private bus operators might rifle through your luggage when the bus is travelling (but this doesn't happen in other countries).
I also agree that if you are carrying an anti-theft backpack, that probably only makes you an even more lucrative target looking at stealing bags!
Since you're carrying costly electronic equipment, a better investment would be a backpack that is actually waterproof, with isolated compartments specifically for laptops if you can find one. Don't skimp out on this because depending on when you travel (rainy season in SE Asia can last months) or if you travel by boat on any stretch, that's the kind of protection - from natural elements - that you will need far more.