One of the criteria to get either a single entry or multiple entry tourist visa in the UK to visit Thailand is to show that you have a balance of £5000 in a bank account for atleast 6 months before application.
It can be more and for longer but anything less will guarantee you being declined.
I had a 1 day overstay in my passport and was declined the 5year elite visa last year during the height of the covid pandemic, i was already located within Thailand though.