Anonymous participant 760 not relevant doesn't matter about the interest, it's about have min balance of 500k at all times, then they have nothing to query. Let's face it if you can't keep at least 500k thb in your account or equivalent in another account then really you shouldn't be in Thailand 500k is nothing, just keep it in whatever account you choose, interest, low interest etc as long as you always have that sum, you can run the risk and only have 25k in your account but that could lead to awkward question on entering again. Immigration can cancel any visa if they see fit to do so, just not worth the risk. Anyway, everyone is free to do as they so decide
Immigration aren't asking you for money that wouldn't be legal but they can ask for proof of funds under what ever visa you have and the rules under that Visa. Immigration are all powerful they can decide who enters or doesn't. They are a separate dept from Ministry of Affairs.
Just keep at least 500k THB in your Thai bank account, if you get questioned at immigration, seems unlikely just show them the balance on your mob app. Proof of funds is the most important criteria