Yes they can request to see 20,000baht in cash prior to your entry bank statements are not accepted but only been asked once in 25 years of visiting twice every year but it's thailand and no surprises if someone is asked to show it we must remember entry to the kingdom is not a guarantee it's all down to the IO infront of you at time of entry Chokh di
Immigration is open on 2nd but your issue is as of 1st you are on overstay if you get caught out between 1st and when IO opens again you may have a bigger problem Chokh di
If a thai national can do that job you won't be getting it if they can pay 20k baht why they going to pay you 50k baht for same job its simple your dreaming
There is no 30day visa for Thailand there is a 60 day tourist visa which you apply for in your own ciuntry prior to departure if not you will enter the kingdom on a 30 day visa exempt if your a passport holder of a country that is part of that alliance with thailand you can extend that once only by addional 30 days at thia immigration for 1900baht but you will need to provide the appropriate paperwork to receive the visa exempt extension of stay chohk di
It may not be of any help but I found Jomtien/chonburi immigration very easy to deal with earlier this years was in and out job done had everything they required on hand was told to come back at 1.30 pm to collect passport did that job done in 1.5 hours maybe I was lucky Chokh di