Where the law stipultes that an agreement must have written evidence and be signed by the liable party in the contract . This includes lease of immovable property for a period of not over 3 years; agreement to sell/purchase immovable property or some types of movable property ; sales contract of other movables worth over 500 Baht ; loan agreement for over 50 Baht , and surety contracts . A contract with written evidence means an agreement made in writing , regardless of that he owes someone 50 Baht , the paper beconmes written evidence and the loan contract is legally complete . Without such written evidence , the loan contract is not enforceable in Court of Law .