Hi, I would like to ask if vendor has signed the booking form but he/she has added a clause that I am not agree. Within how many days i can cancel the booking and get back my earnest deposit? Your answer is highly appreciated. Thank you.

What do you mean by that, the clause can't be added simply. There's valuation of the S&P lawyer and standard template from the Bank Lawyer if I'm not wrong.

let's say both parties counter sign beside the "added" clauses... will this agreement be deem void?

Hahahaha...where there's an added clause as you mentioned, it could actually amount to a counter offer isn't it? If an offer was countered the earlier offer shall be deemed void. I'm not sure how this added clause actually put in for your case though. If anything, it's better for you to check with a lawyer and give them all the details. 

About the cancellation of booking form, as far as I know, most of them actually works only if the purchaser can provide a Bank rejection letter or two. But it very much depends on the clauses stated in the booking form. And you might not get a full refund. 

Better check with an attorney. From my understanding of Contract Law, what you said is most likely amount to a counter offer. Keep me updated if you did consult an attorney. 

Just my 2 cents, correct me if I'm wrong. 

@Ted thanks for sharing