I'm having an idea to develop a health care assistant that can suggest remedies to cure health related ailments. I thought it could be better if it can understand regional languages like Tamil, Malayalam, Hindi etc, to provide better insights. Is this possible with IBM Watson Assistant?
Those regional languages are not (yet) supported by IBM Watson Assistant. For reference, this is the list of supported languages for IBM Watson Assistant.
It is possible to switch between languages during a dialog. The IBM Watson Natural Language Understanding service supports Hindi, Tamil and Malayalam. You could use that to at least detect in which language the bot is ask and react and maybe ask if it is ok to continue in another language or provide some basic help.