This paper presents a three-dimensional foundation numerical model of Thailand's historical building, the Wat Khao Sukim Pagoda. The Pagoda's high reputation is due to the fact that it was constructed through donations from the public. The purpose of the research is to analysis the differential settlement and define the capable layer to transmit the load from structure. Numerical analysis will significantly contribute to the construction and mitigate the impact of any potential differential settlement. The present study is using PLAXIS 3D to model the ground surface and to analyze the settlement of the complex foundations of the Pagoda, which is loaded by varying column load. Back-analysis of the single pile load test was performed to verify the soil parameters and the results of the numerical simulations were in good agreement with settlement data reported in the field. The numerical analysis showed the settlement values in Zone 1 (shallow foundation) were in the range 0.05-0.43 mm, in Zone 2 (short pile foundation) were in the range 0.42-1.98 mm, while Zone 3 (long pile foundation) had a settlement range of 0.82-1.25 mm. These results were considered acceptable due to the modes differences in values that the differential settlement did not exceed 0.75 ins or 19 mm as recommended by ACI, 2017 and ASCE/SEI 7-02, 2013. Also, Weathered Granite layer is determined as an effective layer capable of transmitting a significant load of higher than 50%.