Besides “rent” and “girlfriend” you don’t really mention how much you spend on each expense. Did you have some visa costs in that? Do you mainly eat western food? Do you mainly take taxis for longer distances? $2k would be enough for most people but it really depends on how you spend your money.
If you have a Bachelors degree (legal requirement in Thailand) and you fall within their preferred age range you may get a teaching position and a Non B visa and the school usually has a bank they prefer to do business with. They will usually assist you in opening the account. Having the Non B visa and work permit will usually make it easier to open a bank account at whatever bank you choose as well as getting a post paid SIM card with the phone provider of your choice.