I heard from a very reliable high ranking immigration officer that there are going to be a lot of changes in immigration procedure soon. My take on this is because Thailand must somehow integrate with the other ASEAN countries to be ready for the ASEAN "common market" who mostly follow the standard procedure of most other countries as far as tourists are concerned.
The first casualty will be visa runs and instead you will simply go to an immigration office to extend your visa every three months. I think they will leave retirement, marriage and employment visas as they are. Tourist visas will be two to three months extendable up to a maximum of 6 months in a calendar year. This is what most countries do and also Singapore and Malaysia. If you stay more than 6 months you are considered domiciled for tax purposes and have to pay tax on your full years income. (This is standard in most countries). Up to six months is the period when someone can be defined as a genuine tourist. In many countries you can not stay more than 6 months unless you become a resident. Since in many countries including Thailand it is very difficult to become a resident it means you can only stay 6 months. Australia and New Zealand for example
From another source I also gathered that Thailand was not at all keen on young people (under 50) staying here for more than 6 months without jobs and question why they are not working for a living and suspect many work here illegally or sell drugs and are involved in prostitution etc. So they now can restrict tourists to 6 months and say that they are only complying with the regulations in other ASEAN countries. Please note that this is what I think will happen. Others may have different views on this matter should post them.

This is only speculation. Until a reliable source can be quoted this discussion is closed.