Years ago we flew from BKK to PEN on Thai using stand-by ID tickets.

My wife was on a Thai passport and didn't have a visa for Malaysia, which apparently she should have had as she didn't have a confirmed reservation out of PEN. A hurried conference between Thai Airways and Immigration, resulted in a revalidation sticker showing a confirmed reservation being attached to the return flight coupon. Once Immigration waved us through, the Thai Airways lady promptly removed the sticker.

For years afterwards I kept a couple of reval stickers with my passport, in case of need.