From what I know most of it is listed by the banks, as for condo's it's difficult unless you know someone there but I have seen a notice posted on the door of a condo next door but one from our condo, when it eventually come on the market for sale a friend of mine was interested to buy so she asked me to go with her, one of the said owners worked at the bank she kind of kept in the back ground I got bad feeling about it something dodgy going on, she also got bad feelings and didn't buy plus the were asking 500k baht more than others in project.
as they say buyer beware.