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Forest cover in Thailand had been decreased from 53 to 28 percent in 1961 to 1989. Thai government issued logging ban policy from 1989 until present, then forest loss is significantly decreased. Forest land had been changed to plantation and community areas. Consequently, Thailand loss more than 534 lives and 73 million USD of casualties on landslide from 1970 to 2007. This study is aiming for analysis the effects of root reinforcement on the watershed area for slope stability. Three different types of land use on the Mae Phrong-Mae Phun watershed were selected for comparison. This area was suffered by landslide in 2006 causing the loss of 75 lives. The area loss more than 63% of the forest to orchards and residential areas from 2000 to 2016. Three areas of land uses; original forest (F201), orchard (A401), and an old landslide area (F201-M103) are selected. Soil strengths with root reinforcements and the factors of safety (F.S.) of each land use were calculated. The root spreads and root densities on 1×1m area with 0.1m soil thickness on slope are considered in the models. The severe condition of prolong and heavy rainfall as occurred in 2006 with the saturated soil condition was assumed. The forest area (F201) had the highest average F.S. of 1.730. The F.S. on F201-M103 and A401 areas are not significant different of 0.976 and 0.982, respectively. Using the small grid size in the model could help to identify locations for potential landslides in the study area. [ABSTRACT FROM AUTHOR]