From The BBC Article Cited:
"Opponents and activists have argued Mr Prayuth's term began when he was junta leader. As military leader, he seized power in the May 2014 coup and then appointed himself prime minister of the new military government in August 2014.
That means his term should end this week, his critics say.
However his supporters say his term only began in 2017 - when a new constitution came into force - or even after a general election in 2019 that saw him retain power.
Under those terms, he could technically continue serving until 2027 - if he wins an upcoming general election."
Doesn't Seem Clearcut One Way Or The Other...So... Wait And See...