The 26 December 2004 Indonesian tsunami was the third known global tsunami and reached every distant corner of the globe. An effort has been made here to evaluate the effect of this distant tsunami in a limited area model domain. The effect of distant tsunami has been simulated through an open boundary condition in a Cartesian coordinate shallow water linear model. The open boundary condition is applied to simulate the tsunami propagation when it is assumed that the tsunami is generated far away from the region of interest. The computational domain covers the region so that the 26 December 2004 Indonesian tsunami source is well within the model domain. First, the initial disturbance of the tsunami source are examined along the western open boundary of the model domain and then the boundary condition is formulated and adjusted in such a manner that the effects of tsunami due to the source along the coasts are same as the effects due to the formulated boundary condition. The response of the open boundary condition is investigated along the coastal region of Peninsular Malaysia and southern Thailand. The results are compared with the data available in the website and a very reasonable agreement is observed.