My suggestion would be to get a good Thai lawyer to check it out for you. It so much better to be safe than sorry. If you don't know anyone, then I am happy to recommend one I have used many times before. Just send me an e-mail. No problem Mr Chang.
My suggestion woudl be to get a profesional Thai lawyer to take the copy to the land office and get it checked by them. Easy and not too expensive. If you need a recommendation for a lawyer, just e-mail me. Much better to be safe than sorry.