My 5mths old boy have started sleeping thru the night. Last feed will be around 7pm-8pm, and that will drag until the next morning 8am-9am. At times not wanting to drink instead he wants to play. Is this normal?

I think your baby sleeps well, satisfied after feeding therefore can sleep all night long. You are lucky! From what i read, babies can sleep through the night at age between 4-6 months. During the day, monitor his feeding and look for signs of dehydration if he really doesn't drink much. Since he is busy exploring, let him play first then offer milk after each activity.