British passport , over 50.

I’m looking to fly to Thailand one way , get my 60 day at airport immigration then extend 30 at immigration . In the mean time I’ll deposit 800000 and wait for it to season 2 months @b4 I apply for my 12 month extension/ retirement visa.

Now the question is… I know I’ll need to book an “ exit” flight out of thailand in order to enter Thailand on a one way flight from uk….. but that exit flight will have “expired” when I apply for my retirement visa/ 12 month extension . Will it flag up at immigration whilst I’m applying….