These structures are used to talk about purpose. So that is more common in informal speech and writing. Both these expressions are normally followed by modal auxiliary verbs such as can or will.
- I waited for an hour so that I could meet him.
- She is staying here for six months in order that she can perfect her English.
- I started early so that/in order that I wouldn’t be late.
In an informal style, that can be dropped after so.
- I have come early so (that) I can talk to you.
Present tenses are sometimes used to refer to the future after so that/in order that.
- Send the letter today itself so that she gets/will get it before Friday.
- I am going to make an early start so that I don’t/won’t get stuck in the traffic.