@Phyu *****
Thank You for your helpful reply.
As you have university related study with your Ed Visa, Just be sure you have a re-entry permit to re-enter Thailand. Your most recent entry stamp is in your Old passport...
IF you leave Thailand and have not transferred the Ed Visa, be sure to have the old and new passport with you.
Getting the Ed Visa transferred to your new passport is BEST. Suggest you ask your local Thai Immigration office in Chiang Mai for their assistance. ...
Show them the course of study documents.
And I suggest you have the course documents with you upon re-entry if you are questioned by Thai Immigration Officers.
And have you registered with Thai Immigration office in Chiang Mai your current Address with the filing of the TM30?
I would start with Chiang Mai...
And if needed, then go to the Thai Immigration office which issued you the Ed Visa.