Don't worry if people can seem rude. It's just that even if you weren't English, like me, it would be a weird question. I had never seen a question like that so don't blame people for being surprised and don't worry, we'll figure your problem out !
Actually, it's quite simple. As means "like" and "Has" is the verb "to have" when you use the third pronouns (she, it, he) :
I have
You have
She has
He has
It has
You have
We have
They have
Has is only used as a verb when you mean it's yours or someone's. It shows that you own something, it's yours, not anyone else's.
In your sentence :
I am requesting, on behalf of the Board, that you, has our Regional Member, support our cause.
Ask yourself a simple question : In here, do you want to use the verb "to have" do you want to show people that someone or something owns something or someone else. Actually, you do not or shouldn't do, at least.
As is used as "like" ! Examples :
As a police man, you must be correct and polite
As a student, you should study more and work hard
As our Regional Member, you should support our cause.
You say what the person or people is/are.
I'm not English so it's hard to explain but I hope I'll have helped you a bit, don't hesitate to reply ^^
NOT A TEACHER