A340-500
Probably the most comfortable (and quietest...) long-haul aircraft is the A340-500. Singapore to NYK non-stop, 19 hours, easy-peasy.
Of course, if you are sure your passengers will be entirely comfortable sitting four or five hours from a suitable airport on one engine, the A330-200 shorty will do 7,250 nm.
The'll both carry 250 pax, or up to 350 in sardine-class.