Maestro

There are other ways aside the phone to do the TDAC.

24 May plus six months is 24 November. On the date of arrival in Thailand, your passport will have a remaining validity of six months and 22 days.

Yes, the OP's girlfriend and daughter can go through the fast lane at BKK, if they meet the criteria outlined by the airport authority. https://suvarnabhumi.airportthai.co.th/service/facility/detail/820

Already discussed and clarified in this topic: See this post, for example: https://aseannow.com/topic/1358135-thailand-digital-arrival-card-tdac/#findComment-19741392 No new topic needed for it.

No amendment of the current Immigration Act would be needed.

Removed an off-topic post about how the poster would design the form.

No. With the the current design of the form, it could not and would not be a problem.

There is also this topic about the passport use by dual nationals: https://aseannow.com/topic/1305176-immigration-news-for-all-thai-dual-citizens/?do=findComment&comment=18315531

Why not use the Thai passport and name for buying the ticket and enter Thailand as a Thai citizen, using the automatic gates? No TDAC and boarding pass necessary for Thai immigration.

Thank you. That's interesting. An immigration fine of 2,000 Bath, with receipt, for the late submission of the TM.30 notification is irregular. If your wife still has the receipt, it would interest me to know exactly what reason for the fine is shown, in Thai, on the receipt.

Removed an abusive post.

Leaving any required field stops me from proceeding to the next page. Source: https://tdac.immigration.go.th/arrival-card/#/tac/arrival-card/add In the example above, I failed to fill in the fields "*City/State of Residence" and "* Phone No.", then clicked on the button "Continue" and got the pop-up message "No data or Insufficient data" Regarding your question "what fields do you have to leave blank", the answer is "none, but I am free to leave any and all fields without a red asterisk blank. As another member has suggested, the TDAC site is already up and running for you to try it out, even if you do not intend to arrive in Thailand within the next three days.

Your choice of the terms "What they want to know" and "is asked for" are unfortunate, as they do not provide full clarity. The TDAC form has essentially two types of fields: Fields that require the entry of data or the selection of an item from a pop-up list. If such a field is left blank, I cannot proceed to the next page. These fields are marked with a red asterisk. Fields for which data entry is not required. I can proceed to the next page even if I leave such a field blank. The field "Visa" is an example of such a field for which data entry is optional: regardless of whether or not I enter data in it, I can proceed with data entry into subsequent fields. These fields are not marked with an asterisk.

As I wrote in the post you quoted: Leave the field blank.

Anyone with a pioneering spirit arriving in Thailand already before the official launch date of 1 May 2025 can do the TDAC within three days prior to and including the entry date and surprise the immigration official with it, ie with the printout of the PDF document you get by email within minutes of submitting the data. Then keep it as a memento of your adventure.