Hay has only one form in the present tense. The verb “hay” means there is or there are. It meaning depends on the noun that follows. It is used to call attention to the presence or existence or something. The following expamples illustratrate this point.
Hay muchas personas aquí / There are many persons here.
Hay mucho dinero en el banco/ There is a lot money in the bank.
There is an idiomatic expression that is used with the verb hay: hay que. It means one must or it is necessary to and it is followed by an infinitive. The following examples illustrate this point.
Hay que estudiar / One must study
Hay que dormir/ It is necessary to sleep