What I was saying was that I never bring more than that in cash, and use ATMs to top up. Would you wander around Ireland with €500 on you? I wouldn't and never carry serious cash wherever I travel.
Eating out in Thailand and Vietnam is cheaper than here, can be waaaaaaaaaaay cheaper if you want to eat in local establishments and off the fantastic stalls. Backpacker areas are cheaper than the touristy places too.
The most expensive meal I've had in either of those 2 countries was Retaurant Bobby Chin in Hanoi where 2 courses plus drinks came to $80 for 2. This is Hanoi's Patrick Guilbauds price-wise. I think the cheapest meal I had was in Thailand and was about $4.
After that it depends on what you want to spend your money on. If you're staying in resorts they tend to be expensive, but wander out to eat and drink and you'll be fine. Spa prices in resorts in Asia are bargains compared to here though, I highly recommend that.
Do you want to get clothes made? Most places are cash only. We paid $60 a suit in Thailand, $80 in Malaysia and $45 in Vietnam.