Malaysia, Indonesia, Singapore, Thailand, Brunei, Cambodia, Laos, Myanmar, Vietnam and the Philippines form a political & economical association referred to as Association of South-East Asian Nations i.e ASEAN.
AirAsia has a launched pre-paid ASEAN pass for about Rs 10,000 ($160) valid for 30 days and 10 credits. The 60 days/20 credits version is Rs 18000 ($290). Taxes and add-ons such as check-in bags need to be paid when you book the actual flights.
A one-way flight between any 2 destinations in these countries will require either 1 or 3 credits. The way it works is you buy the pass & redeem the credits to book the flights
The details are well-laid out here.
From India, AirAsia flies to Kuala Lumpur from 6 cities (Bangalore, Chennai, Hyderabad, Kochi, Kolkata, Trichy) and a return ticket should be anywhere between Rs 10,000-15000. If you are flexible with dates and patient to book way in advance, look out for the periodic sale for some sweet deals.
Adding up an additional Rs 5,000-10,000 for taxes/add-ons + Rs 5,000-10,000 for visas, one can fly around South-East Asia for just about Rs 30,000-45,000.
This is a great product from AirAsia leveraging its wide network in the region.