This cross-sectional study investigated the prevalence of work-related low back pain (LBP) and its associated risk factors among 446 home-based informal garment workers in the northeast of Thailand. The results from structured interviews indicated the six month-prevalence of LBP was 44.39% (95% CI = 39.67–49.02). The significant risk factors of LBP were included no ordinary exercise (ORadj = 1.6; 95% CI = 1.01–2.52), members of family had LBP (ORadj = 2.19; 95% CI = 1.90–2.37), working hour ≥8 h per day (ORadj = 1.6; 95% CI = 1.98–2.61), repetitive movement (ORadj = 1.84; 95% CI = 1.12–2.99), prolonged sitting >2 h (ORadj = 2.65; 95% CI = 1.62–4.34) and no change of posture each hour (ORadj = 1.97; 95% CI = 1.18–3.30). It is concluded that no regular exercise, nature of repetitive work and prolonged sitting, and behavior of unchanged posture each hour are contributed risk factors to LBP. In order to prevent LBP in this home-based worker, ergonomics training and worker’s health promotion should be routinely implemented.