yes, you could be right, normally when you hold a valid visa, the airline doesn't ask for an onward travel proof. However I guess the ticket "within 60 days" is needed for the METV visa application, which is a whole different story
there is no guarantee an airline will accept a bus ticket for an onward travel proof, because they could say that the bus will only get you to the border but not across it 😃 The only safe and 100% guaranteed onward travel proof is a "real" cheap one way ticket out of Thailand. You can use Air Asia from Hat Yai to Kuala Lumpur as a perfect proof. Why do we hear about "onwardtickets" soon to get refused? Because they are not "real" flights but just reservations, one can clearly sort them out in the TIMATIC system, and since the beginning of the year the fine for violating IATA rules has risen five-fold, it can be up to 10.000.- USD per case.
get a Thai passport for the daugther. (she automatically is a Thai citizen if she has a Thai mother). Then exit Thailand on your foreign passport, making your stay permits invalid (hopefully you haven't bought any re-entry permits, because an exit under an existing re-entry permit would not invalidate the stay permit and you would have to ride it out until the "admitted until" date) Okay so exit, and both of you re-enter on your Thai passport. Problem solved
and you shouldn't have a problem to show 3 months of seasoning the 800,000.- THB, since you wrote that this is already your second application for the 1-year Extension. Of course saying that you didn't touch the money in the meantime
well, if you take the same care you took about the TM30, I have little hope. Your landlord has to register you at the immigration per TM30. Maybe Immigration accepts the rental contract and signed copies of the blue house book and the Thai ID card of your landlord for your self-filing the TM30. You will definitely find out only when you ask your immigration, and not the readers of this Facebook group
there are 88 immigration offices in Thailand, you got a choice. What's more extensive: loosing the stay permit because of immigration harassment, or moving and solve the issue?