You can wait till CM. You can extend anywhere you actually stay at that moment.

Chiang mai is strict in checking TM30. At least at the main office they are.

I would say. Start with a real visa. 60 days tourist visa. Best opion.

Follow the date on your multiple re-entry permit. Which is 26 september. Its not voided so still valid.

You need a consent letter from your wife to travel with your child: ref Thai embassy in Bern :

1.2) Only one parent travels with the child/ren; please provide

- An official relationship document, e.g., birth certificate

- consent letter* from the other parent/legal guardian with a copy of his or her passport OR if you have sole custody, you must provide a copy of custody papers OR if the other parent is deceased, you must provide a copy of the death certificate.

Get a proper visa for longstay if you intend to longstay. For some not working, studing or being retired in Thailand it means the only option is a more expensive Elite visa.

No one cares/checks about your ticket dates. Fly in before the expiration date and get your 60 days stamped.

In Chiang Mai you can apply for a extention of stay 45 days in advance.

Chris Latinoinbkk

Its not only the financial issue. For me the paece of mind knowning i can go anytime and not need to worry about getting my 2th or 3th re-entry in time made me just get the multiple. Only if i am sure its only 1 time i do a single. But nothing wrong to look at the financial side.

Chris Latinoinbkk

Its a little confusing because the request form asks for a date. But you can ignore that. Its valid with the same duration of your visa.

You can get a multiple re-entry permit giving you a unlimited amout of re-entries. How could you know all dates in advance? No a date is not required. I do this many years. Sometimes multiple but lately in covid times a single is sufficient for me.