I live in Australia so just any flight is a long haul flight. When I was younger I used to just suck it up and fly economy but as I've gotten older it just takes it out of me.
We flew to Italy 10 years ago and my feet were swollen for 5 days. I haven't flown economy long haul since.
If you can afford it shell out for Business Class. You won't believe the difference.
Another tip - if you're going to fly via LA, spend a night there near the airport and then get a direct flight to Singapore.
At least you will get on the plane well rested.