Looks like a figure-8, Tetraodon biocellatus to me. The crossing over yellow markings are making the "8" shape, anyway. I have to admit, for a second there I was going along with T. fluviatilis, but I don't think so. With T. fluviatilis the yellow bands tend to run across the body from side to side, rather than in loops.
Hope that helps,
Neale