But is UA getting a revenue premium on this route? A full cabin does not translate to profitability. Same for BKK. It's like "we're losing $1 per seat, so we'll just add more"

Bigger or more isn't always better - higher margins in a smaller business is preferred to running razor thin margins on a larger operation.

Japan, Korea, India and Taiwan are higher margin Asia markets. China is for now a higher margin market but a rapidly shrinking one. Vietnam might become one given the potential transfer of some China traffic to Vietnam.

Manila doesn't appear to be if the premium cabin is running almost empty. I don't see Thailand bucking that trend. We can assume United has "run the numbers and sees potential", but we've been down that road before with new routes that fizzled, failed to meet potential, or the pricing was off and sent customers to other options.