Hi : As far as I know there are hardly any facilities in Suvunarbhuni for kids. which is not good. The airport was built to a very tight budget and thus things such as this were left out. Also as far as I know, unless you have one of the travel cards which get you into a range of lounges worldwide, you cannot pay to get in. There are plenty of snack places near the E,F,G gates which are more 'child friendly' than the up market food places in the centre of the airport - places like Burger King etc . Maybe not what you are looking for I guess!! There are information desks before immigration which may be able to help, and its worth asking there as well.
Sorry for the bad news, and best of luck

There are a few facilities in the airport though they are fairly spread out and mainly centre around restaurants and other eateries. Try the lower ground floor at the front of the airport for a large number of good restaurants, some of which are very toddler friendly. Do be aware that this area can get busy at times and so it might be worth checking out the food hall on the upper floor which can be reached by either a lift or a long escalator from the rear of the departures concourse. This is quite a nice place which is less busy than the other restaurants and which is quite spacious. This would be a good place for kids as there is a viewing station upstairs which provides a good place to see the planes. The prices are reasonable though not cheap especially by Thai standards. There isn’t a swimming pool or other recreation area such as at Singapore’s Changi Airport, but these types of facilities are the exception rather than the norm anyway!

Food options are aplenty at the Suwanaburmi airport in case you have a picky eater on your hands--from Japanese or Chinese rice meals, to deli sandwiches to Burger King and Dairy Queen fast food near gate E's. There is also a lot of space to run around, and some Thai inspired cultural items like statues and a small house-structure that will probably be fun for kids to look at. I believe changing rooms for children/parents are also available in the airport.

That being said, if you are looking for some organized play area for your child, that may be a tough one. The leisure activities are mainly for duty-free shoppers and international cuisine restaurant lovers as the brands, shops and cafes are many and diverse!!! Though this is more "adult" entertainment.

Hope this helps you make the most of your stop!