Importation of GM plants to Thailand is prohibited except GM corn and soybean only for the industry supply propose. In 2019, Thailand imported more than 3 million tons of wheat, which MON71800 is the only GM wheat that appears in the ISAAA approval database. A screening test for identifying GM wheat contamination in imported wheat to Thailand is necessary. CaMV35S promoter and NOS terminator are the main elements mostly found in GM plants. To distinguish GM wheat from other GM plants, event-specific detection of MON71800 is needed to be employed with ACC-1, wheat endogenous control. Tetraplex Real-Time PCR is a technique that can detect the CaMV35S promoter, NOS terminator, event-specific MON71800, and ACC-1 in one reaction. In GM wheat MON71800 screening service, certified reference material (CRM) of MON71800 is essential for use as a positive control. Unfortunately, MON71800 CRM has not been commercialized. Therefore, the authors have developed an in-house plasmid that contains the elements of the CaMV35S promoter, NOS terminator, event-specific MON71800, and ACC-1. Moreover, the authors reveal specific primer and probe sequence and detection conditions by Tetraplex Real-Time PCR. This study is useful for screening tests of GM wheat and economizes by reducing the cost of CRM and chemical use in Real-Time PCR reaction.