I arrived here since 2022 doing visa extension every month until 2024 August when i got DTV. They can ask you questions but give then reasonable answers and required documents. That should be okay.
Very safe. If it wasn’t, how come there are lots and lots of tourists and immigrants here day by day and year by year. Fear wouldn’t get you anywhere. The amount of $ to bring totally depends on you. Minimum 2-300k thb would be optimal. But still totally up to you.