I've questions,

When I leave my current company, I know my work permit gets expired right then.

 

• For how long I can stay in Thailand after work permit getting expired?
• How long it will take a new company to create a new work permit, I believe the process should be easier as I already had the work permit?
• Any other things should I know when moving from one company to another in Thailand with work permit.

You work permit is not the main issue you can have. If you are on an extension of stay based upon working issued by immigration it ends on the date you stop working.

The only way you can change jobs without leaving the country is if you new employer applies for a work permit and obtain a work permit application approval letter. With that letter and supporting documents from them you could apply for a new extension on the date your current  one is canceled by presenting a termination letter from you current employer. Then you new work permit could be issued when your current one is canceled.

@ubonjoe

 

I've heard that once you leave job and work permit expires, you have 7 more days to stay. Is it correct?

 

17 minutes ago, Myke11 said:

I've heard that once you leave job and work permit expires, you have 7 more days to stay. Is it correct?

Not unless you are getting your extensions at the one stop center for BOI companies and etc.

The 7 days to leave went away at normal immigration offices years ago.

You can though go to immigration a few days before your termination date and immigration will post date the cancelation to that day.