Do I need a re-entry permit for my O A multi visa when leaving Thailand?

When you leave Thailand on an O A multi visa, you will need a re-entry permit if you wish to return without losing the validity of your visa. Without this permit, leaving the country can result in the voiding of your visa status. If you obtain a re-entry permit and then return within the specified time, you should be able to receive another 90 days upon re-entering.