that’s unfortunate if that’s the case that their requirements changed in March. I did the rounds last year asking at various banks and branches on a special tourist visa with a 9 month condo lease. Got knocked back many times but at all the Bangkok banks I went to they kept quoting the letter from embassy.
It would be a good idea to find out why you were specially declined the regular 30 day extension. Perhaps you needed to put "Tourism" as the reason for that extension if you asked for it first. I can kind of see why they might had declined you if you had stated the purpose for that extension was to see Thai family.
Go Bangkok Bank Silom branch. They deal with a lot of foreigners. Make sure you get a letter from your country's embassy (you may need to pay for this service) confirming your address in your home country and thailand. With that letter you shouldn't have any hassles.
Are you certain about this? I follow the other Thai visa forum very closely and the experts there have discussed this extension at length. Perhaps its just visa exempt that its only 1 or the other. Will need to do some more digging. For single entry tourist visa the advice is 60 + 30 + 60 = 150 day
Once married (or have a Thai kid) you are able to get 60 day extension to any entry for visiting Thai family after using the usual 30 day extension. So tourist visa gives you 60+30+60. An entry with visa exempt allows you 30+30+60
Bangkok Bank on Silom Road as Gary mentioned is the place to go. They may ask you for the letter from your country's embassy that confirms your address in Thailand. So if your embassy can write you the letter (probably for a consular fee) then that is all you need to take to Bangkok Bank along with your passport.