Hi i own 49 percent in a thai LTD, VAT registered and possibility for 1 WP that i am giving away. I have been working in it for 18 months. At what date do i need to leave the kingdom after transferring the shares. I have a visa extension for a year and a WP?

The visa extension(if based on work) ceases to be valid on the day you stop work which is also the day you should leave unless a 7 day extension is applied for from immigration.

The work permit and extension are not tied to your ownership of the shares. Decide with the new owner when your employment should terminate. Get the appropriate documentation from your "employer", go to immigration on the termination date and your extension is canceled. At that point, if you meet the conditions for an extension on other grounds (such as 60 days to visit your wife) immigration may or may not be willing to give you this at the same time. More likely, an extension will be denied and you will be given 7 days to leave the country on payment of 1,900 baht.