In may the best places in India would be North India or North East.
You can also go for trekking in Himachal Pradesh this will more relaxing holiday to beat the heat
Depends on what you’ve already traveled or are looking to travel to, but as may is hot in india it should be a cool hill station I suppose.
It could be the North east, Kashmir, Himachal Pradesh or can also be somewhere in south like ooty or munnar. Happy Traveling :)