Beautiful crab!
Most Pseudothelphusidae crabs are Neotropical (Central and South America), but as shown, there are genera and species from the old tropics, including the Parathelphusa shown from Indonesia.
Species I am familiar with (genus Pseudothelphusa from Colombia and Ecuador) are 100% freshwater, living in small mountain streams, far, far from the ocean. But other species inhabit streams closer to coastal areas, including tide-affected areas, thus brackish.
Most species would need a dedicated aquarium as they are highly predatory. In addition, most species are severely endangered due to human habitat destruction.
Absolutely beautiful.
Thank you for posting it!