If flying in, you'll definetly need a passport. Land borders are hit and miss with border pass. For Cambodia I think you need to be resident in the border province to be eligible. Just use the passport, much easier and Thai passport holders don't need visas for Cambodia.
the visa that was mentioned is available also to children who have a thai parent. So not necessary for the child to have thai citizenship to get that particular visa. But as said, under 15 she won’t be fined for overstay anyway
Being a foreign wife married to a thai husband there is no monetary requirement. You can extend her stay in thailand every year very easily. If you are earning more than 30,000 baht per month, after three years of marriage (one year if you have children) she can apply for thai citizenship.
I’m a dual citizen myself. It should be no issue - however all names in both passports and on the vaccine records should match. For instance if your wife was vaccinated in Europe then her name on those records should match the thai passport name otherwise they won’t issue the thai pass/COE
oh that’s good to know that 60 days is available on that basis then and will save a bit of hassle! I know the years extension requires money on the bank but I presume the 60 day one doesn’t?