As
@Bra****
said banked money is not an issue. As you have no prior history entering Thailand they’re not going to ask you to show cash.
The onward ticket is up to the airline. You’ll see a split difference of opinions on here. Some get away with no onward flight but many are asked - by their airline. If you don’t have one you may be denied boarding. You could ring and ask your airlines policy on that or Google “onward ticket” and get a throwaway one for around $10.
If you’re planning on staying over 45 days then you can either apply for an extension at a local immigration office (1,900 baht approx €50) for a further 30 days to get 75 days total or apply for a tourist visa and get 60 days on arrival (also extendable once so 90 days total) for £30 approx €35.