Does a visa extension in Thailand start from the application date or the original visa expiration date?

When applying for a visa extension in Thailand, the extension begins from the date of application if the application is based on a different reason than the original visa. However, generally, extensions related to the same reasons as the initial visa will extend from the original visa's end date. It's important to review the specific conditions on your extension sticker, as it will detail the permitted duration in relation to your entry stamp.