Multipeak negative differential resistance (NDR) molecular devices are designed from first principles. The effect of NDR is associated with the non-linear Stark shifts and the electron localization within the conductive region and contacts. A deep I(V)-curve well is formed when the aromatic molecule, containing intramolecular hydrogen bond, is connected to each lead by the double-branch contacts. This effect occurs at the same voltage where a single-junction case exhibits only a flat step in the current characteristics. The multipeak oscillations arise from the mutual effect of the Stark shifts located at the electron-rich contacts and parts of the molecule – this opens the route for further tailoring the desired properties.