Singapore Airlines my friend.. Their Economy product is very good. Comfortable seats, good grub and ace service. Tickets me be on the expensive side, but with a little bit of planning, you should be ok.

The routing i presume would be LAX - SIN - BKK. Transiting thru SIN is a breeze and so no worries on that front. it's going to be either a 777 or 380 out of LAX and a 777 on the SIN - BKK leg.

A family member flew HKG - LAX bout a month back in economy and she said it was super cramped..Have flown SQ long haul on multiple routes and it's always been very comfortable flights.