Just flew the LAX-SIN but same aircraft. I would really go for the front cabin, but understand what you are saying. The downside is that everyone passes by you going to the snack area/toilets. My wife and I had the last seats in the back of the first cabin and they were just fine. Had toilets right behind us, but not as noisey as I thought and most of the traftic comes from the back cabin. The absolute best are the front row seats in the front cabin with tons of leg room. If you haven't flown Exec. Econ. it was great with Singapore Air when you add in the service level. Think of it a 300 passenger aircraft with less than 200 on board! It's interesting that your flight schedule is only about 30 minutes longer than the LAX flight!