I found this handsome fellow in a bathroom in Borneo. As you do. It's a four-lined tree frog (Polypedates leucomystax). This species is widespread in South East Asia, living in just about all habitats—including bathrooms. Polypedates is a relative of the flying frogs (Rhacophorus). Like them, it builds a foam nest from whipped-up mucus, in which it lays its eggs. The nest is usually attached to a leaf overhanging a body of water. When the tadpoles hatch, they drop and swim away.
This individual made no noise but the call was described to me as 'a big, watery fart'. So there's another reason to encourage wildlife in your house. Something else to blame.