Not sure I want to bet, but here is an interesting Wikipedia excerpt on Thailand's coup and the events on May 22, 2014:
Date
22 May 2014; 8 years ago
Location
Thailand
Result
Successful military and police takeover
Caretaker Prime Minister removed
Yingluck's caretaker government dissolved
2007 Senate dissolved
2007 Constitution repealed
Military junta, the NCPO established
Prayut endorsed by Bhumibol as NCPO leader and Prime Minister
2014 interim constitution by NCPO enacted
It clearly says that on May 22, 2014 Prayut was endorsed as Prime Minister by the King.
Now, when the King says that Prayut is PM on that date I don't think Prayut has much legal wiggle-room here, given how much he and Phalang Pracharat proclaim to revere the King and the law, and so on and so forth... Still, he does have Wissanu...