Is it 45 days before to renew extension  is it 45 days before in Bangkok 

Sometimes 

Yes 

Yes, in Bangkok you can apply for an extension when you have 45 days or less left on your current stamp.

 

Yes CW is up to 45 days early.

Your 12 month extension will start from current expiry of permission of stay.

In other words nothing to be gained by leaving it late. 

 

Here is link for appointment 

https://bangkok.immigration.go.th/en/onlineservice-and-publicguide/

 

Note: can only be made up to month in advance. 

In Chiang Mai it is.