Why not offer at the airport or border-crossing a choice, to qualified incoming visitors, an option of 30, 60, or 90 day visas? Set the costs at say for 30-day free, 60-day 1000bht, and 90-day 2000bht? You pay with a Credit card or baht to immigration and get your passport stamped; off you go. This would be more streamlined, less hassle, and easier way to entice more tourists to visit Thailand.