I have overstay for about 8 months and now going back to Singapore on the 25th this month via Don Mueang airport.

Is there a difference between departing from Suvarnabhumi and Don Mueang?

What is the procedure at the airport, do I check in first then proceed to pay the overstay fine or should I clear my overstay issue first before checking in?

Are the new overstay rules in place yet?

Thanks

No difference between airports.

You you pay the fine at departure immigration after you check in for your flight.

The new overstay rules have not been approved yet.

Thanks Ubonjoe, should I go to the immigration counter as usual and let them guide me or should I find the office myself to settle the fine?

Normally there is an officer that guides people to the lines for the desks. If you tell them you are on overstay they will direct you to the office to pay your overstay.