This paper focuses on the performance of prefabricated vertical drain (PVD) improved soft Bangkok clay in accelerating the rate of consolidation by using vacuum and heat preloading. Large scale consolidometer tests were performed with PVD improved reconstituted specimens using surcharge preloading (PVD only), surcharge combined with vacuum pressure preloading (Vacuum-PVD) and surcharge combined with heat (Thermo-PVD), respectively. Subsequently, the flow parameters were back-calculated based on Hansbo (1979) method by expressing in terms of the horizontal coefficient of consolidation (C_h) and the ratio between the horizontal hydraulic conductivity in undisturbed zone (k_h) to the horizontal hydraulic conductivity in smear zone (k_s) or (k_h/k_s). The C_h were 1.93 m²/yr, 2.23 m²/yr and 4.17 m²/yr for PVD, Vacuum-PVD and Thermo-PVD, respectively, with corresponding, k_h/k_s values of 3.0, 2.7 and 1.4, respectively. Thus, the Vacuum-PVD can increase the horizontal coefficient of consolidation, C_h resulting in faster rate of settlement at the same magnitudes of settlement compared to PVD. The Thermo-PVD can increase further the coefficient of horizontal consolidation, Ch with the associated reduction of k_h/k_s values by reducing the drainage retardation effects in the smear zone around the PVD and consequently, faster rates of consolidation were obtained.