Yes you can and you can have it set so that both you and the Thai have to sign in order to make withdrawals. This type of account is useful if for example you have a half Thai child and want to save in a bank account for them even though they are not old enough to hold the account themselves
This recently caught me out. You do need to update the bank book on the actual day of application. If you haven't had any transactions on that date it won't update to the correct date. You need to actually have a transaction take place on day of application before submitting application inorder for the bank book to be updated correctly
You should be careful with this we have just lost both families that live next door to us due to the situation with only 1 guardian visa being allowed per child. They couldn't find a way to get the other parent back in so have had to leave