I just booked an economy award ticket through the UA website putting the infant's information in the search as well. PHX -> SEA --> NRT --> BKK on US Airways/United/Thai Airways. Return is BKK --> NRT --> LAX all on Thai airways. Fees were $65. There was an option to go on Singapore Airways on the return flight but fees came up to ~$400.

I called UA to ask about additional fees for the infant and he said that nothing else was required and that her name was listed on the ticket as a lap child. Is there something I should do to make sure that I don't get hit with exorbitant fees when I show up for the flight in November? Should I call Thai Airways?

Thanks for any info.