There are tropical deciduous trees that lose the leaves "in response not to seasonal temperature variations but to seasonal rainfall patterns" [Wikipedia] but the Japanese maple is not one of them.
The tree is dead. Black spots on the trunk are never a good sign.
These types of deciduous trees cannot live in a tropical zone like yours. They can survive for a few years but in the end they are doomed.
They can stay inside during the warm months (always better outside though) but they need a...
Please read this article on Wikpedia. There are plenty of charts backed by research that confirm human-caused climate change is real. There is no denying it if you look at the facts.