I am a regular on the PRG-AMS-PRG route with CSA, and I have Gold status (that is as far as you can get in the OKplus programme).

Last month I had a regular economy ticket (basically there are three types of economy (premium, regular and value - I had the middle one)). I was booked on OK624 to AMS (departing at 19.05 from PRG). I arrived at the airport at 16.00 and I could still make the OK618 which left at 17.05.

The lady at the check-in counter asked me whether I wanted to change. I said if it is for free - why not. She was then as kind as to leave her station, walk over to the ticket counter with my reservation confirmation and have a discussion with the lady there (at which point I was very impressed with the service). On coming back she informed me (blushing when she told me) that the change would be EUR 230 (approx $300). Less impressed, as that is close to a single fare business class. So I decided to wait two hours (they have a nice lounge in Prague, by the way - accessible if you are Elite Plus in any SkyTeam program).

Summarizing:

1. maximum status in their own program does not help
2. not paying the lowest fare does not help
3. having a sympathetic check-in assistant does not help

So I wouldn't put your hopes too high. You might be lucky of course, maybe they will shift you for free when they are overbooked as they regularly are on the PRG-AMS route (especially the Monday morning OK616 as well the Sunday afternoon OK618 are notorious). I could not determine from your question whether you were departing from Prague, but I have the impression that outside of Prague they are slightly less strict with the rules.