Drowning is a leading cause of childhood deaths in Asian countries. Children in primary school have a high rate of fatal drowning. These fatal drownings commonly occur in natural water bodies near the child’s residence. The 2004 Thai National Injury Survey reported a higher rate of drowning death in rural settings. While swimming skill is recommended to decrease drowning risk, there is a lack of information on factors contributing to a child’s swimming skill. This study assesses guardians’ perceptions of the swimming skill of rural primary school children and identifies associated risk and protective factors. A cross-sectional household survey was conducted during August-September 2009 in rural communities of Chiang Rai province, Thailand. We analyzed a total of 633 interview surveys completed with guardians of primary school children. Results revealed that less than one-fifth (19%) of the school children (age 6-12 years old) could swim. Multiple logistic regression showed that children who can swim are more likely to have attended swimming lessons Ratio [OR] = 23.95; 95% CI = 12.21-46.98); be 10-12 years of age (OR = 4.15; 95% CI = 2.35-7.30); be male (OR = 2.82; 95% CI = 1.67-4.77); have had self-reported life-threatening submersion experience (OR = 2.14; 95% CI = 1.10-4.12); or be the child of a guardian who can swim (OR = 2.10; 95% CI = 1.25-3.44). The results highlight the need to provide swimming lessons targeting all children beginning in the younger age groups. Local resources in natural water sites may provide a place for safe swimming lessons in rural areas.