Sorry to take so long to reply. The larger ones are temples, originally built as Hindu ones, if I remember right, then slowly taken over as Buddhist ones. There actually is a lot of crossover,between those two religions - both believing in "multiple paths" to spiritual goals. SE Asia began as Hindu then became Buddhist, for the most part. You can go inside the temples and they contain statues, carvings on the walls, all kinds of stuff. I don't specifically remember seeing tombs inside, but there could be.
Anyway, the smaller tea bell shaped ones are generally stupas. Those usually contain a Buddhist relic inside or underneath. Generally, there is not a way "inside" the stupas, but hey! I plan on hidden passages, so why not? It is pulp after all.
Sorry the memory is a bit hazy, but it is an amazing place to visit. Very off the beaten path for tourists.
Mike Demana