Near the southeastern edge of Wachira Benchathat Park (see map) is a large enclosure that houses Bangkok's only butterfly garden that I know of. The big oval-shaped garden hosts dozens of species of butterflies as well as some small birds.
A pair of 'dead leaf' butterflies
There are of course plenty of flowers as well as other enticements to get the butterflies to land and feed where you can see them. One of the more interesting examples you can see here is the “Orange Oakleaf” or “Dead Leaf“ butterfly (Kallima inachus). With its wings folded together the insect can easily be mistaken for a dead leaf. But when the wings open the top sides are a deep purple color with an orange stripe.
Admission to the garden is free. It is open daily from 8:30 am to 4:00 pm.