Getting the typed AST isn’t possible without OCaml, but there are some loose plans to expose a subset of the relevant parts of the typed AST as JSON via the @rescript/tools package.
A hack, but what you can try today is running the doc command from @rescript/tools on your file: rescript-vscode/tools/README.md at master · rescript-lang/rescript-vscode · GitHub
That will dump out JSON using the typed AST for that file. It’s intended for driving doc generation, but you might find what you need in there already.