As Covid extensions are gone for good, the next cheapest option to stay in Thailand is border hops. Here in this thread I propose to share information on border hop agencies, prices, requirements, personal experiences etc.
I personally know of Meesuk Travel Agency (you can google by their name) that does single day border hops to Cambodia from Bangkok. The price though is not very cheap - 3500 baht for their service plus 1000 for a Cambodian visa. As far as I remember, before Covid the prices were much cheaper and the visa fee was included.