I am an Indian passport holder living in Japan. I am travelling to India through Singapore and returning back to Japan via the same. Since the arrival and departure are at different terminals, I came to know that visa is essential. Is it possible to get a multiple entry visa from here? What should I do for that?
Singapore's Changi Airport has a total of 3 terminals, numbered Terminals 1, 2 and 3. (There was previously also a "Budget terminal", however this was closed down several years ago)
All terminals are connected air-side, both by walkways and by "Sky Train", and thus there is no need to exit immigration to move between terminals.
The only exception to this may be if you are travelling with luggage, and on an airline(s) that will not allow the luggage to be checked through to your final destination. In this case you will need to exit immigration to collect and re-check your luggage.