- The research’s objectives are to measure highly-pre cise coordinates from GPS signal of post-seismic motion of Sumatra-Andaman earthquake in the study area, and to compare the motions with those derived from a visco -elastic model. Time series of 5 campaign stations during January 2011 and February 2013, together with data during January 2012 – Januray 2013 from SPRB continusous GPS station in Suanpueng, Ratchaburi reveals that in horizontal all stations moved in souteast-east direction with the velocity around 28 mm/yr. In vertical, height time series show both uplift (Kanchanburi 4.9 mm/yr, Petchaburi 6.2 mm/yr) and downlift (Chonburi -15.3 mm/yr, Nakorn Nayok -6.1 mm/yr and Ratchaburi -15.3 mm/yr) while SPRB CGPS moved upward with a velocity of 1.5 mm/yr. The visco-elastic model forecasts downl ift motion in 2012 with rates of -1.8 mm/yr and 2.2 mm/yr depending on recurrence period. Although vertical motions of certain GPS stations conflict with those from the model, the study shows that magnitude of postseismic motion is smaller than those of other facto rs such as groundwater extraction and consequently the effect of post-seismic motion is n ot worrisome. However, the time series length is only 1-2 years and disturbed by relativel y large magnitude of local short-term variations which cannot yet be discerned or average d out so further monitoring of at least 2-3 years should be continued in order to achieve a more reilable trend of plate motion.