@Daniel ****

As long as the visa is valid, check the date valid until or enter before date ON the visa, you get 60 days on entry.

The Immigration of the airport works to stamp people in or out Thailand,

On Suvarnabhumi airport there is an office where you can apply for a Re-Entry Permit if you want to come back before your current stay ends.

Just tried it out and after making an account, log in and start to apply for a new visa.

I filled in as above but got this message, so clearly it does not work

Depending on your current stay inside Thailand and with 400.000 Thb in your bank account you can apply for:

Conversion into the Non Immigrant O visa based on marriage

Extension of Stay based on marriage and when that is stamped into the passport the Multiple Re-Entry Permit to travel during the year.

OR

Visit the Thai Consulate in HCMC Vietnam or Savannakhet Laos who issue the 1 year Multiple entry Non Immigrant O visa which gives you 90 days of stay on each entry.

IF you're inside Thailand using the Visa Exempt Entry or the Tourist Visa you can visit your local Immigration Office to apply for a conversion into the Non Immigrant B visa.

Yes, but no need to use the on-line websit.

Your Extension of Stay with the Re-Entry Permit are registered in the Immigration Database. Just using a new passport does not change your fingerprints, face, name, dob, gender, nationality etc, only change your passport number. It will be linked.

If you want to enter before 24 July you have to discuss with the Immigration Officer to use the NEW visa and not the Re-Entry Permit.

@Pat***

Or you can enter using the new passport and the new visa after 24 July. Bring the old passport with you just in case questions are made.

Or you can enter before 24 july but than you have to ask the Immigration Officer to use the new passport and the new visa.

I guess these are the what if, if what and if you have or if you do not have possibilities. Save travels.

@Patrik *******

You can re-enter Thailand before 24 July, using the re-entry permit and visit the Immigration before 24 July to apply for a new Extension of Stay. It is not 1 month in advance but during the last 30 days of your permitted to stay period.

To make it complete :

No grace period if using the app or online, it must be done between 15 days before and due date.

It can be done 15 days before due date by old fashioned mail.

OR

between 15 days before and 7 days after due date in person at the Immigration Office.