For a retirement visa it is fairly common now for people to change from a 30 day visa on arrival to a Non Immigrant visa such as a retirement visa without leaving. This is providing you are 50 years of age or above and have the financial criteria to satisfy the Immigration Officer. If you extend the 30 day visa on arrival with a 7 day extension and wish to change to a retirement visa, this cannot be done. The 7 day extension given states on the visa that no further extension of stay will permitted. So, if you find yourself in this predicament, the fastest and easiest way to clear this problem would be a one day visa trip to Cambodia which will give a 15 day visa at the border. This will then allow you to convert to a Non Immigrant visa and retirement visa in Thailand.