The petition was submitted on April 2019 by 72 MPs.
It accused Prayut of issuing an executive order on the implementation of the MRT Green Line project to intervene and interfere in acquiring concessions from government agencies.
At the time he issued the order, Prayut was head of the junta National Council for Peace and Order.
The court ruled that his executive order violated Section 184 and 186 of the Constitution, which warranted termination of ministerial status. However, it said that constitutional provisions on the termination of ministerial status only cover people holding the position of minister at the time. Since Prayut vacated his position as prime minister at the 2019 general election, he was not subject to disqualification from office.