Guarantee and mortgage are used as security under Thai Law. The Civil and Commercial Code of Thailand sets out the criteria for the creditor to call for debt payment from the guarantor as well as the consequences if such criteria is not followed. For mortgages, there maybe a circumstance where the mortgage property, with the mortgage attached, is transferred to a third party. In such case, the third party may repay the debt and redeem the mortgage. This article discusses interesting supreme court decisions on legal basis on calling the guarantor to repay the debt and the right to redeem the mortgage by a third party according to the Civil and Commercial Code of Thailand.