From my own research. I intend to park at car park zone 2 or 3 which is just across the terminal(less than 100m walk) All zone from 2-7 can park full day at 250b/per day. If i go away for more than 8 days, i think getting a taxi to and from airport is better cost wise. Assuming one is from Pattaya or nearer. I remember the last time i parked there, they issue a small hardly readable receipt. Best is to check with them.
https://suvarnabhumi.airportthai.co.th/service/airport-guide/detail/All_parking_zones_at_Suvarnabhumi_Airport