Yes the immigration office is at IT square, there are 3 forms you need to fill in the TM7 and two others, yes you will need your passport, a recent passport photo, copy of your passport and incoming stamp on your passport. Cash to pay. there is place where you can get copies done next to the office, if you go early before shopping center opens, enter through the 711 store. its a bit confusing. you can catch the train there. hope this helps
Stick a sign on the front door, "It pays to be quiet and respect your neighbours. Short term stay is illegal in Thailand and if you make a noise the police will be called. You have been warned"
We own a condo in Sukhumvit Bangkok and when we were looking the agent told us if you are looking to rent location is important. We rented our out for a few years with good returns before we retired and spent more time in Bangkok. Important to look at how well the block you are looking at has been maintained some better than others.. You need to understand that it is not easy to re-sell condos in Thailand, it's not like home. We are currently selling our condo which is well priced for quick sale yet we have only had two viewings in six months. PM me if you have any specific questions, I will try and answer.