Is one hour layover sufficient at Singapore Changi Airport (Indian citizen travelling from US to India)?

Airports don't come better than Changi -- in terms of efficiency and in terms of helpfulness.

Airlines don't come better than Singapore Airlines. If it can be done within a 1-hour layover, then it will be done at Changi.

However:

1. It's a ridiculously-tight connection
2. It's a pity not to have a decent layover at Changi -- the world's best airport to have a layover at
3. You'll almost certainly have to go through security again at Changi, though they're very efficient and very nice about it
4. If your flights are all on the same ticket Singapore Airlines will see you get to your destination even if you miss the connection through no fault of your own. If your flights are not both on the same ticket, then the airline's under no obligation to do anything if you miss the connection.

If Singapore Airlines is willing to sell you the connection, they are confident you can make it. If, for whatever reason out of your control, you miss your second flight out is their contractual obligation to get you into the next flight to your destination.

In practice, 1 hour is plenty for Changi because:

• you only see immigration if you attempt to leave (or enter) the airport (because ‘Singapore domestic flight’ doesn’t make sense the entire airside part is just considered out of Singapore)
• when you arrive, you will directly enter the ‘departure’ area of the airport (there are no separate arrival lanes)
• you will have to go through security again but security is decentralised at Changi, meaning one set of security checkpoints handles about five gates. When I was there this year, in most cases there was only one flight due to depart soon behind one security checkpoint so no trouble at all.

In case you are a slow walker, note that Changi has automatic people movers that connect the far wings of three terminal to the central part. There are also a number of conveyor belt walkways designed to speed up your trip.