whats the earliest time, and the latest time,to transfer from a multi o to a extension of stay(retirement)all criteria okay.

You can apply any time during the last 30 days of your current permission to stay. It is best to apply early in case immigration require additional documents. You will not lose any days by applying early - your extension of stay will start from the end of your current permission to stay. Remember if you plan to travel during the period of your extension you will need to obtain a re-entry permit from immigration to keep your permission to stay alive. 1,000 baht single entry; 3,800 baht multiple entry.

You can apply any time during the last 30 days of your current permission to stay. It is best to apply early in case immigration require additional documents. You will not lose any days by applying early - your extension of stay will start from the end of your current permission to stay. Remember if you plan to travel during the period of your extension you will need to obtain a re-entry permit from immigration to keep your permission to stay alive. 1,000 baht single entry; 3,800 baht multiple entry.

cheers thaipoon,to clarify,if i do 2 border runs,ie,back in los with (ovisa)in sept,dec border run,march border run,apply in may for extension,as long as rules not changed be all above board.

Yes you can do that. Just make your last entry while the visa itself is still valid.