I think the problem is to call createVertexBuffer at each frame (maybe several times). It would be better to create the vertex buffer once and update it (with ThinEngine.updateArrayBuffer, which uses bufferSubData), but I don’t know if this is possible, I don’t know this voxel engine.
On the other hand, do you know Divine Voxel Engine - Voxel Engine Made With Babylon.js - Alpha 1.0 Out Now ? Maybe it could be an alternative choice.