We examine exotic properties of the charge-ordered (CO) state which has been found even at room temperature in the 3:1 organic compound (NT) 3GaCl4 (NT=naphtho[2,1-d:6,5-d']bis([1,2,3]dithiazole)). First we analyze the band structure by using the extended Hiickel method and reveal nontrivial bond modulations along the staking axis: a strong trimerization on one chain and a dimerization on another chain. Based on this lattice structure, we examine the origin of such a CO by using a two-chain extended Hubbard model. Within the mean-field approximation, it is shown that the CO pattern observed in the experiment is well reproduced by taking into account the intermolecular Coulomb repulsions. Furthermore we analyze the variation of the energy by shifting the phases of density-wave order parameters and find that the characteristic energy for the melting of the CO state is quite small, ΔE = 20 meV. Based on these analyses, the anomalous non-linear conductivity found in the compound is also discussed. © 2008 IOP Publishing Ltd.