We will be traveling on 4thJanuary (domestic). What facilities are available food and drink wise. Just in case there are no holdups and we get there early.

You won't starve...the usual suspects as to Fast Food and some Thai offerings also.

The floor one or two above domestic departures (in between the domestic and the international terminals) has a tonne of restaurants and food options. Plenty of tables and chairs to sit also.

http://donmueangairportthai.com/en/603-donmueang-restaurants