Extrusion grade of PBS (Nature works®PLA2003D) with a density of 1.24 g/cm3 and a melting point of 165 ºc was use as polymer matrix due to its biodegradability and commercial availability. Fine particles of CSR (Paraloid™ BPM-520, Dow Chemicals Company) were applied to PLA and PLA/rubber wood composites for toughening purpose. The bulk density and the average particle size of the CSR are 0.4 g/ cm3 and 250 nm respectively. Flour of rubber wood (Hevea brasiliensis) was obtained as waste from a sawmill in Ayutthaya, Thailand. The wood flour was further grinded by using a ball mill and sieved to the top cut sizes of 500 µm.