We did a similar cruise a few years ago, and the weather was very nice(hot), the three days cruiseing will be good sunbathing time,although it may be a little chopy.The India stops are smashing, and you will find Dubia a shoppers dream.
Nothing like the Atlantic folks. Not an over exciting leg for visits, though Phuket can be fun, but certainly one for sun and balmy calm seas.
Not sure about the sea state, but having lived in Singapore which I love dearly, it is not renowned for endless hours of sunshine. It is however very hot and humid and can rain heavily most days, the rain however is short lived, but nil desperandum, when the sun does come out it's lovely.