Skin injury is a growing issue among older adults, especially when admitted to an intensive care unit or long-term care facility. Skin prevention is a key point in dealing with this issue, and prompt and effective screening instruments should be used to identify risks and start preventive interventions and care. This descriptive study aimed to translate and examine the psychometric property and implement the Perineal Assessment Tool for incontinence associated dermatitis risk assessment. The English version was translated into Thai following the international guidelines from the World Health Organization by the bilinguals. From May to June 2023, 119 patients from the semi-intensive care unit were included using a consecutive sampling method. The research instruments included the demographic questionnaires, the original English version, and the translated Thai version. The Thai Version had a content validity index, an index of item-objective congruence, a Pearson correlation coefficient of percent agreement, the Pearson correlation coefficient of the interrater reliability, the Kappa coefficient of interrater reliability, the Pearson correlation coefficient of the intra-rater reliability, and the Kappa coefficient of intra-rater reliability ranked from 0.75 to 1.00. The 21.95% had a high risk of developing incontinence-associated dermatitis, which was associated with females, the length of stay in hospital and semi-intensive care unit longer than or equal to four days, receiving antibiotics, disease severity greater than or equal to 20 points, the albumin level less than 3.8 g/dl, and neuropathy and brain disorders. In conclusion, this instrument has high validity and reliability and can assess patients at risk of incontinence-associated dermatitis. This tool will help with early risk detection and guide for planning to manage various risk conditions to prevent dermatitis instead of taking care of them after the skin has already been damaged.