Check hotels on the west side of the airport (King Kaeo Rd). I've stayed at pretty much every one of them with exception of the Amaranth as they are crazy expensive. I'm not sure if they are even open. Their going rate was around $300 a night.
My to go before departure hotel for the past couple of years is Miracle Suvarnabhumi hotel. Around $50-60 a night. The problem with that location is that there are almost no restaurants. Just 7-11, street food carts and one or two restaurants miles apart.
North side of the airport (Lat Krabang Rd) has pretty crappy hotels. Price range $18-$30 but plenty of restaurants. Used to stay there before departing BKK in 2015-17. Main reason were the local restaurants. However, once I've tried hotels on the west side I stopped going to the ones on Lat Krabang. Grab delivery or just took Grab to restaurants on On Nut Rd.
In the worst case scenario you are 15 minutes away from BKK terminal from hotels on either side of the airport.