I'm going to Vietnam for a few days, then leaving the country for a few weeks, then coming back for a few days. My question is about visas. I'm a U.S. citizen.

Getting a multi-entry visa sounds kind of confusing, especially since it'd need to be a multiple month one. Actually, getting a visa at all sounds confusing, but a 30-day tourist visa sounds the least confusing. So I was thinking of getting a 30-day visa, single-entry, here in the U.S. for my arrival (involving a few days in Saigon). Then sometime during my 3 weeks of traveling around southeast Asia, probably in Phnom Penh, I was going to get another single entry visa for my departure (involving a few days in Hanoi, a month later).

Does this work? Can you use two single-entry visas in a short period like that? Or am I better off figuring out how to get a 60-day multi-entry visa?