Thailand forum

For 70 days I'd be planning on about $2000-2500 for daily expenses ($28-35/day). You can go a bit cheaper in places like Chiang Mai and smaller Laos towns, and leave some margin for the ocassional splurge, like the pricier bungalows down on the southern beaches. You'd be pretty brave to carry that sort of cash around the whole time, so carry a large portion of it in travelers checks and/or get the ATM card out once in a while and take out the max daily limit.

Vietnamese Dong and Laos Kip are standard currency in those respective countries, although US dollars are accepted and even prefered in some higher-level hotels and some western-style restaurants. In Cambodia the USD is pretty much the standard currency of tourism but Riel is more appropriate for smaller towns and small transactions.

There are increasing numbers of international ATMs in Laos and Cambodia, and there are lots of them in Vietnam, and one on every street corner in Thailand. Sure there are associated fees but you get something for it - convenience and safety.