Can you be force pooled in Oklahoma AFTER you previously signed a lease with another company?
Generally, No if you have a standard lease. The one that would be pooled would be the "other company". Unless you excluded specific formations or depths that the pooling covers or something like that.
Usually what happens is they ran the mineral owner's report before your lease with the other company was filed. In some cases I have seen the lease with the 3rd party only define one tract and the owner also had ownership in another tract within the same pooling area.
When in doubt, make an election at the pooling. But I would expect that you get dismissed from the pooling before it is complete.