Day-roost usage, nocturnal activity, foraging area, and social structure of the painted wooly bat, Kerivoula picta, were investigated at the village of Khon Kaen in northwest part of Thailand. The bats mainly preferred dead banana leaves as day-roosts, while leaves of sugar cane or broad-leaved trees were occasionally used. They frequently switched their day-roosts every one to four days. Families numbering three bats (adult female, adult male, and young) were found in February, June, September and October. However, such families were not found in November and December when pairs constituted 64% of the total number of captured bats. Most of the pairs roosted together in day-roosts, and did not change their partners during the survey period each year. Foraging areas between contiguous pairs did not overlap each other. Foraging areas averaged 6.1 ha for males and 5.6 ha for females. Kerivoula picta fed chiefly on relatively small-sized web-building spiders. Most of the pairs changed partner every year. The recapture rates of newly banded bats after one year averaged 20%, and the oldest ages recorded were five years for females and four years for males.