You make the route as India-Kuala Lumpur - Singapore - India. Or India - Singapore - Kuala Lumpur - India. Make the tour of at least 6 days, 4 for Singapore and 2 Kuala Lumpur. For sightseeing in Singapore use TripAdvisor and Buy tickets from Sea wheel travel in Chinatown, Singapore. They sell the cheapest tickets. For transport in Singapore use Public transport, it's the best. In KL use grab taxi for transport, it's cheap and door to door. For attractions tickets use Klook.