There is no such restriction or rules for clothes to wear in Kerala. If you are still pondering over what to wear in Kerala, cottons are the ideal option. Kerala has no laws regarding how to dress up, yet, it is better to cover up and look decent as it may hurt Indian sensibilities. Kerala has a hot and humid weather through the year with little variations in temperatures. It is best to have cotton and light clothes with yourself.
The people of Kerala are very simple by nature and feel offended if
someone offends their feelings. Thus, avoid any kind of public display
of affection, wearing provocative clothes, etc in Kerala. Also, do not
forget to take your sunglasses, hats and lots of sunscreen!