"have to" and "had to" are used with do...

[Hardwork]

In negative and questios ,"have to " and "had to" are used with do,does,did:as
He has to go---He doesn't have to go--Does he have to go?

I read this statement in an English grammer book and was confused because of following reason please explain me the same
Over here "he" is third person singular so we should use "has" right ie it should be
He doesn't has to go--Does he has to go?

[Mordant]

It's "grammar."

We do not conjugate verbs that attach to auxiliary verbs, such as "do," "be," "have" and "can." We use the base verb of the infinitive. It does not matter whether we are referring to the first person, second person or third person. If anything is altered, it will be the auxiliary verb itself. Note that modal auxiliary verbs, those without infinitives (e.g., should, could and would), do not change for singular or plural subjects.

If the verb is have, it is "do(es) have."
She/he does have and I/we/you do have

If the verb is "run," it is "do(es) run."
She/he does run and I/we/you do run

If the verb is "have," it is should have
She/I/we/you should have

If the verb is run, it is should run
She/I/we/you should run

"Should, would, will, can, and could" all work the same way.
"Do, be and have" all work the same way. These last three change to suit the subject, and then they attach to the main part of the infinitive, which does not budge.

[Hardwork]

[Mordant]

Indeed, "have" is the choice.