Transfer of existing visum with EOS from an old to a new passport.
Easy peasy.
1.) Get your new passport 😉
2.) Copy ALL pages of your old passport.
3.) Copy picture page of your new passport.
4.) Fill out ½ an A4 from immigration.
5.) Go with all of the above to immigration within 1 minute.
6 ) About ½ an hour later, I had my stamp in my new passport. It is actually FOR FREE. In my case even with a new 90 day limit.
7.) TM30 notification: I did a new one online but the officer said that it is not necessary, the old printout would be OK.
Go eat a celebration noodle soup for 40 THB, and think about how old you will be in 10 years when you will have to do it again.
NB. Immigration Korat today.
TLDR : Answer Summary
Transferring a visa from an old to a new passport in Thailand is a straightforward process. First, obtain your new passport, then make copies of all pages of your old passport and the picture page of your new one. Fill out a form at the immigration office and submit your documents. The transfer is typically free and can take about half an hour. However, procedures and fees may vary by local immigration offices, so it's wise to check with your specific office ahead of time.