Desi if you are not connecting onto another flight at Changi upon arival and you feel you badly need a shower I recommend the handicapped washrooms where you can happlily wipe down with a face cloth before heading down to Immigration and your hotel.
Please don't blame the airline just because they do not have an arrivals lounge due to the set up of the airport.
When travelling in J I always get up 3 hours before landing and use the planes washroom and wipe myself with a facecloth and shave as well so I look awake and smell good for the SQ girls.
