My daughter used to do this and we would tell her we wake up when the sun comes up and go to sleep when the sun goes down. Now she reminds me when bed time is.
My daughter did that a few times too lately. We gave her some water or a little bit of milk. We told her that it is still bed time and that she has to stay in bed. While she stays in bed she can listen to an audiobook this helps to put her back to sleep.
Try a “ok to wake up clock”? I have never tried it but I know people that this has worked for them with there early rise kids.