So,

My visa exempt stamp expires soon, and I am flying to KL and back on same day, to receive another 30 day stamp. (my first time)

My final air ticket out of Thailand is booked for late April, but changes are possible on this ticket for a fee, and it states this on the print-out I have.

I'm sure many people have made this border run, and was wondering if I'm likely to be asked to present an onward ticket, either here or in KL.

If I am, would I be ok to show my existing ticket, explaining that I will either change this ticket to fly out withinn the 30 day period, or if not, do another border run.

I'm hoping the fact that I have paid for an outward journey is enough, or, to be safe, should I buy another cheap ticket to KL for a date within the 30 days?

Any comments, advice or experience of this situation much appreciated, thanks.

Within Asia proof of onward travel is normally not asked for.

Telling the airline you will be traveling with might give better answers.