I, a US citizen, am planning a trip to Vietnam for an academic conference to which I've been invited. The conference web page suggests getting a tourist visa and points to two websites which allow one to purchase a tourist visa (more precisely a visa-on-arrival). However, the US State Department says that Vietnamese officials require foreign visitors to engage in only the type of activity that their visa is appropriate for.
Note that Vietnamese immigration regulations require foreigners entering Vietnam to undertake only the activity for which their visas were issued.
This implies that I won't be allowed to attend the conference on a tourist visa; I would need a business visa. Is this correct?
If not, can anyone point me to more authoritative information (i.e. directly from the Vietnamese government) stating that it's okay to attend a conference on a tourist visa?
If it matters, I'm currently working in China, not in the US.