Hotel booking short term should be adequate.

The embassy will decide whether it's enough and request more funding proof if they choose. I'd definitely provide a balance equal to two persons, you aren't supporting a baby or toddler.

Anonymous participant the sponsorship letter is in lieu of the funding, if she has her own money in a bank account in her name it isn't necessary. There is no income requirement for DTV. If the embassy requests further proof of how will she support herself then you can supply a sponsorship letter, your DTV number and a substantial bank statement in your name.

No too old, that said it's pretty easy to get a DTV with a course of some sort, a sponsorship letter, bank statement from the parents for the funding requirement.

What scheme will you apply under? Find a good Muay Thai gym that has a history of DTV approval success and have them guide you.

In country extension? I wouldn't risk it, because anything that can go wrong will go wrong with an in country extension. The account you're showing should be in your name and the balance of a minimum of 500k for 30 days before you apply. Just bounce.

Now that your spouse has the DTV you can apply as a spouse category and reference their DTV number, You can supply your own funding requirement or your spouse can write a sponsorship letter depending on the embassy you're applying through and your financial particulars. You'll also supply marriage license. For the children the exact same process except you'll choose dependent with birth certificates as proof and again a sponsorship letter with the main DTV holders qualifying bank statement. All applications can be submitted through the main DTV holders Thai evisa account.

Probably or whoever signed your work contract.

Which consulate? You can just put a hotel. You're applying too early, three months in advance max. You can apply for your dependent children as soon as your approval completes you then supply your visa number and choose dependent in the drop-down box each child will need a separate application and a separate fee. You can do them all from your online evisa account. Dependent applications are typically approved pretty quickly

It's a requirement, you'll only slow down your processing time by not submitting it along with your other mandatory documents. Where do you plan to apply from?