Actually, there are meal services on some flights. Breakfast is served on flights departing before 9am or so, lunch around 12pm and dinner around 6-7pm. Those are just my estimates based on my own experiences - no idea about the official times. These meals have a hot main course and some fresh fruit. Other flights get a snack - a warmed chicken pastry last time in C. In Y there is a larger snackbox during meal times and a small one for snack.

My favourite for BKK-HKT is TG 921 - on many days it's a 747 or M11, so you can get a First seat and this flight has meal service. I have usually been flying HKT-BKK on TG 222 or TG 920 (F seat on a 747 again) but those flights have no meals. Although 772 C is 2-4-2, it's not half bad for the domestic flights. A330 has probably best C along with 773 after the 747/M11 with a chance for F seat.