I've done this once, although not by mistake but fully intentionally (long story...). A call to AY CS fixed it, they just switched the names with no fees. However, this must have been like 15 years ago. A lot has changed in the industry since then.

I would just fly with the tickets you have. Intra-Schengen it is unlikely that anyone would even check your id. BKK they'll check for sure, but when they're boarding a plane of 300 pax and your bags are in the hold, I don't find it likely that they will try and get you to buy new tickets at the gate.

OTOH, a friend of mine bought AB tickets and absent-mindedly entered first name twice and last name not at all, getting tickets for John John Mr. They made my friend buy new tickets for €400.