Disclaimer : This post is about Bangkok only, where it has become very difficult to open a Thai bank account since 2015. Other province such like Phuket, Pattaya still a good try to open one.
I personally tried 25 banks in November 2017 along the Sukhumvit line bets before finding one except me. At this time I was an expat in Thailand working about my own online business, on a tourist visa. Until now I was using my credit card from France and was paying both side fees, also an account from kasikorn my girlfriend was not using, for small amount. My girlfriend is an officer from Thai navy, so we have given a first try at TMB branch close to his base... Unlucky, we not fall on the right bank officer we attempted to see and they tell us that less Tabian baan (Family register book) or Work permit, it was not possible to open an account under my name. Open one under the name off my girlfriend was possible, but if for any reason the relationship going in trouble i guess i will have only my tears for cry...
Since 2015 the Thai junta enforced the law about foreigner banking because of money laundering (mostly from Russia and USA they said...) Most off Bank was offering a solution for people staying in Thailand on tourist visa, but it was under the ownership decision off each branch management of the bank, by example some kasikorn was allowing you to open it, when the next kasikorn few hundred meters later was rejected you. Mostly it's about misunderstood between the management of the bank and the staff. In Thailand, to show you don't know something, it's like "to lose face", which is not allowed in their culture. So they will prefer to say no its not possible and feel confortable...
Also some management off Bank use that for sell you inssurance package and other product they force you to suscribe for open you a Bank account, most off the time they cant explain you any guarantee off the contract and apparently some going until to do fake offer, a way to got money under the table...
This has happened to us after 3 hours, my girlfriend upset by the lack off knowledge off bank staff and their non sense has going on the kasikorn branch in big c on nut, close to our condo. There they all said less work permit it was impossible to do it cause since 2015 they have to register work permit number in the data. When she was talking about what we read on their website about open an account under tourist visa was allowed, they said not at their own branch. Since i tried again few head office, then city bank, UOB, SCB, Krungthai, and almost all bank company along the sukhunvit line from bearing bts to siam.
Some said i should to buy condo and make a deposit for it, some said i should to make a baby (WTF) some said to put everything under the name off my girlfriend (...)
Finally after being again rejected from SCB at siam paragon, i going to MBK mall alone. There have SCB, kasikorn krungsri and few others at the same floor off phone repair shop. I got rejected one by one until i entry to the krungsri Bank (Yellow Bank).
Allmost passed the door, the security guard asked me what i want. Surprising he not reject me and allowing me to seat. I was not hope much... Then a girl officer was take care off me and tell me i was possible, to show my passeport. On this days i was on tourist extension ( 1 month ). Then to show me a contract off condo rental or house or property act. Contract have to show a minimum off six month left off the lenght off rent, if not they will reject you. They currently not accept hotel adress. Then she going edit the bank book with my information, copy my document, and also asked me how much i want to deposit. There dont have a minimum. She gave me a debit card to use at ATM, they also give a credit card, its depend off them, apparently u need to deposit about 80000 thb the first time. All was cost me 350 thb fees. I got login id to login on the internet Banking. Since everything work well.
One more advice : dont forget to change the phone number linked to your thai account when you leave thailand or let an activ phone in Thailand to a friend or your wife to get the OTP password. OTP password is a security process when you want to do transfert or any operation by internet banking.
Since november 2016 until now i send 6 friends there living in Bangkok and they all got it.