large butterfly, 4" wingspan
Sri Lanka, southern and North-East India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Kampuchea, Vietnam, southern China (including Hainan, Guangdong province), southern Japan, South Korea, Ryukyu Islands. Peninsular and Eastern Malaysia, Brunei, Philippines, and Indonesia (Sumatra, Java, Bangka, Kalimantan and the Lesser Sunda Islands except Tanimbar). In India, along the Western Ghats from Kerala to Gujarat, also Palnis and Shevaroys. In the north from Mussoorie eastwards, to North-East India and onto Myanmar.
I spotted this on a small sand bank beside a shallow stream just off the trail in Nam Nao national park.