Hi there ~
I understand your concerns for your son. I know that autism
is a tough illness to deal with. ABA or applied behavioral analysis would be the best to give your child the therapy that he needs to lead a normal life. The trick is to find out how your child communicates. It is the failure to do so, that makes the life of the caregiver not worth and very hard at times. I also think that getting an appointment at NIMHANS is easy. You go to the CAP (child and adolescent psychiatry) OPD i.e. outpatient department which is in the campus, get yourself registered and get a screening done. Go with all your documents and you should be seeing a resident and subsequently a supervisor who is a CAP psychiatrist
very briefly. An appointment is assigned to you if necessary (for either extensive therapy or evaluation) and advice given regarding medications and therapy. I hope this helps.
Take care and have a lovely day!