Hi. I spent about 6 months in south east asia in 2010/ 2011. I used tsb visa ice. A lot of credit cards charge cash advance fees even if account is in credit. TSB ice does not. That was how I mainly worked with a backup of my BOI laser card (with Cirus at the time). I very seldom (maybe never) had to use my BOI card. Its a big risk though to have cash on your credit card as seemingly it is not protected the same as your debit balance on a credit card. If it is stolen you could lose the money on it. This may be the very same protection as a debit card though.
In relation to you travelling on a BOI debit card. I would not recommend it at all. I am not positive on these figures but I think there is a 3.5 % cash advance fee with a minimum fee for Euro 3.17. I found ATMs in Laos would only give a max of around 100 Euro per withdrawal. Possibly Thailand is similar. Add to this a 1.75% conversion fee. Add to that a fee on the Laos/ Thai side to use the ATM. So on your max withdrawal of 100 Euro you could lose about 6 Euro.
Having some USD in your wallet/ hidden somewhere is a good idea. ATMs in Cambodia gave USD rather than local currency. USD can be spent easily in Vietnam, Cambodia and Laos and to some extent Thailand. In Vietnam I sometimes found exchange rates for paying in local currency rather than USD much higher, once at around a 13% increased rate over the current exchange rate. (Probably not typical but just what I had once in a hostel for tours priced in USD).
I have heard and tried it once or twice that going into a bank branch rather than using the ATM may give you a better rate, may let you withdraw more, and maybe with lower fees. I am not sure though.
Anyway good look, any questions just shout. Enjoy