Widen the airport bottlenecks
I find the data on airport utilisation to be interesting. If it's correct that Suvarnabhumi Airport accommodates nearly 100 flights a day, it would indicate a takeoff or landing every 15 minutes.
This does not appear to be full utilisation, so why the rush to expand? A workflow study should determine where the bottlenecks are - at places like check-in, immigration processing, baggage handling, air-traffic control, ground control and many other locations. This would require the AOT to have an engineering staff with training and working knowledge in Lean Management and Six Sigma. Lean management must be complete, from the top down. There could be some problems and roadblocks caused by politicians.