1. Despite conservation efforts, large mammals such as tigers and their main prey, gaur, banteng, and sambar, are highly threatened and declining across their entire range. The only large viable source population of tigers in mainland Southeast Asia occurs in Thailand’s Western Forest Complex (WEFCOM), an approximately 19,000 km2 landscape of 17 contiguous protected areas. 2. We used an occupancy modeling framework, which accounts for imperfect detection, to identify the factors that affect tiger distribution at the approximate scale of a female tiger’s home range, 64 km2, and site use at a scale of 1 km2 in WEFCOM. At the larger scale, we estimated the proportion of sites occupied by tigers; at the finer scale, we identified the key variables that influence site-use and developed a predictive distribution map. At both scales, we examined key ecological and anthropogenic factors that help explain distribution and preferred habitat use. 3. WEFCOM is virtually only “half full” of tigers, it occupied 37% or 5,858 km2 of the landscape which was largely influenced by the combined presence of all three large prey species; in contrast, site use was most strongly influenced by presence of sambar. 4. By modeling occupancy while accounting for imperfect probability of detection, we established reliable benchmark data on the distribution of tigers. This study also identified factors that limit tiger distributions; which managers can then target to expand tiger distribution in WEFCOM and guide recovery elsewhere in Southeast Asia.