considering you already have non-o opening of the bank account you should qualify. They will try to make it harder than necessary but do persevere; lease (properly signed each page) helps while residency letter from Immigration remains necessary. The letter must be addresses to each bank, a general letter will not do. Another letter will be required for driving licence. Make sure TM30 is issued to you wherever you are staying.
none of us speak Thai and immigration does not expect you to. If you tick the boxes (get the fact sheet from your IO) there is no need for an old boy’s network.