Do I need proof of accommodation to extend my visa in Thailand for another 30 days?

@Eh ***************

You should be able to go in with the 1900 baht and your passport and don't forget that little square TM6 form that you got when entering Thailand though Immigration - hopefully you didnt lose it. You will also need a passport photo and photocopy of your passport page. There should be a photocopy shop nearby Immigration to do that at. Robert answered your accommodation question.

@Eh ***************

No need to book hotels in front, you apply at the nearest Immigration Office and can use your current address

@Eh ***************

as I understand it you have done approximately 90 days with one standard extension already done. In which case the 60 day covid extension maybe your best option now.