Where did you read you need to upload a rental contract from a house in Thailand?
It is not mentioned on the application website
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Why change your current stay into a DTV. living 8 years in Thailand should be done with 1 year Exensions of Stay, which give twice as long stays and as you already did you know you do not have to travel every 180 days to jump the hoops of the wrong DTV.
BTW TM30, with other words you residing at an address in Thailand becomes invalid when you leave the country, as you do not reside at that address anymore.