Optical diffraction tomography (ODT) is broadly employed to study 3D structures of transparent objects in a stain-free manner. ODT is commonly implemented with an interferometric setup, but its applications on mesoscopic objects have been challenging due to its limited phase detection range. We introduce an ODT method capable of producing 3D refractive index (RI) distribution via a single-pixel detector. Our method exploits a single-pixel wavefront sensor to measure two-dimensional complex information of millimeter-scale weakly absorbing objects at various projection angles. The application of the Fourier diffraction (or slice) theorem to the acquired complex images results in an RI tomogram of transparent objects. The experiments with calibrated objects and zebrafish larvae demonstrate its promise for measuring the RI tomogram of large and weakly absorbing objects beyond the visible spectral range.