Never flown Thai before but was curious about what one can expect in J on a 12am departure from HND to BKK.. Will there be dinner & a breakfast or just one and if just one which will it be?

I'm having trouble selecting a seat. It was an award ticket with UA miles but the ticket is confirmed and I see the res. on Thai site. Tried to message on Twitter but there isnt an option to message them. I cant seem to find an 800 number for Thai. I can try United I guess but it didnt let me select a seat for this flight. It did however allow it for the SQ flight that is on the same res.

Thanks