What happens to a Non-B visa if I exit Cambodia and return to Thailand without a re-entry permit?

When exiting Cambodia with a Non-B visa without a re-entry permit, whether the visa is automatically cancelled upon returning to Thailand depends on your visa status. If you have been in Thailand for less than 90 days from the initial issue of the visa, no action is needed. However, if you've applied for an extension at a local immigration office, you must cancel that extension upon returning if you wish to apply for a different extension later. If you plan to travel only on tourist status and do not intend to extend your stay, you can leave it as it is.