better wood for a plinth

I have found a table of oak of 5cm of thickness (2 inches), is good?

Jatoba (brazilian cherry) was not on his list, but would do nicely as would Santos Mahogany- both are very hard and dense.

I am not familiar with working with Eucalyptus, but shy away from thick oak boards. Laminate if you need to use oak as it often has internal cracks and/or voids from the drying process that you may never see. It is a common problem with 12/4 or 16/4 oak.

Maple

Jatoba

Maple then...

in argentina, the options : maple , eucalyptus, oak, your recomendations please

Agree with 4est.

Beech Multiplex Type MU 25 is another option. Once the plinth is built I would thin skin it with Babinga.

I would be really surprised if you cold not get B Birch there, it just may not be called that. Similar products here in the states are:

Apple Ply
Die Board

If I were making one I would seriously consider Panzer Holz.

Babinga