Houses-on-stilts overlook the Caribbean Sea from Tulum’s beautiful beaches, double-decker treehouses tower in the jungle of a Thai eco-resort, and four new treehouses are soon to be unveiled in Charleston. Suffice it to say, these treehouses are well beyond the scope of what your childhood imagination may have pictured for your own backyard, but we’re sure you’ll still be overwhelmingly pleased by these cozy stays. There’s an olive grove in Tuscany with treehouses, a Lithuanian forest…