Friends from Vietnam want to visit Bangkok. They have no clues about the regulations - and me neither.

I assume a passport is the only thing necessary. Can they get a 30 days stamp at arrival, or do they need a visa?

Do they need to show any money, hotel bookings and such?

Any other things to be aware for Vietnamese/Asean citizens?

They have visa exempt entry for 30 days so visa is not required for short visits.

If traveling by air, no visa is required for a stay of less then 30 days (and a ticket out within thse 30 days).

As every tourist, they can be asked to show money of at least 20,000 THB.