kiwiaussie

Would it be an issue in life? Mostly no, except at perhaps the worse possible time, as Heng, suggests. Is it hard to change? No. A quick trip to the district office to get a new ID card issued, and then the next passport the name will be updated.

She entered on her foreign passport, she should exit on it. If she's under 15, no stress, as their is no fine. You should always enter and exit thailand on the same passport. https://www.thaicitizenship.com/traveling-as-a-dual-citizen/

Curious to understand what makes you say that? A certified copy from SB of the RG seems to work pretty well. In any case, once you have an ID card, its never asked for again.

Females married to Thai husbands don't need to reserve a Thai name. https://www.thaicitizenship.com/thai-citizenship-based-on-marriage-to-a-thai-husband/

The best site for this is www.thaicitizenship.com - lots of free guidance there. Also a long running thread here (300+ pages).

Why on earth are you going for residency? If you are married to a Thai citizen then you can skip PR and get citizenship with roughly the same qualifications. Substantially cheaper (5000 baht vs 98,000 baht) and comes with a heck of a lot more rights.

You are misreading the law. This article explains how you are misreading those particular clauses in the nationality act https://www.thaicitizenship.com/thai-dual-citizenship/

Correct - that's the one. They should update their Thai ID when they arrive, and with that, head down to immigration and get an annual extension based on that. This article explains it all a little more: https://www.thaicitizenship.com/thai-ancestry-visas/