The visa requirements are you need to HAVE that money, not only to get the money only for the moment of approval.
Tricks like you did, make it now more and more difficult for others because most embassies now ask you to show you had the money for 3 or 6 months already.
The visa requirement is that you HAVE the money for as long as you visit Thailand.
DTV is not meant for living in Thailand, but by using 180 days back to back stamps for 5 years, legally you do nothing wrong as long as you still comply with all visa rules, but Immigration just does not like it, for living in Thailand other visa are meant.
I think the more your behaviour looks like living in Thailand, the more risk you have IO does not like.
As long as you comply to all visa requirements they have no good reason to stop you, but they know you cannot force your rights.
But even that sometimes does not work. Before DTV when I was in Thailand on 60 day visa exempt and around day 40 we wanted to visit Malaysia for just 1 day because that is within 100 km from where we live, the IO in Pedang Besar refused to let me in because "same day in and out we don't do at this border crossing"
I never found an official rule anywhere that same day in and out is not allowed, but for IO it is a moment to decide if you get new visa exempt, and for DTV the IO also can decide not to let you enter.
You need besides your passport, your visa, your visa stamp and the most recent TM30.
Best to have copies of all because some immigration offices don't want to make those copies themselves.
When you leave the country and come back, most times no checks except from passport and visa, but all visa requirements are still valid so when IO asks you have to prove.
I think it should be mentioned that although with a border hop there normally are no checks the inoitial requirements still are valid.
I know some here say that is not true, but up to now nobody from this group could show any official document that proves that once the visa is applied the requirements become void.
I asked this at the embassy where I applied for the DTV and they told me the complete list with requirements is still valid on every re-entry and it is up to Immigration if they want to check.
Nobody says you can not rent it out, but you need a Thai employee to manage this process, I agree it sounds stupid. My Thai lawyer warned me that when I am working on the house I live in in Thailand, like painting this officially is not allowed, because I do not own it, and I am not married with my partner.