you get a visit from immigration to your home a few days after application. They ask a few questions, take a few notes, compare photos submitted with actual, ask witnesses a few questions and finally take outside the house with the house number. Same procedure as last year
in my case they were only interested in letter from bank about thb 800,000.- confirmation but they put a slip in my passport that 800,000 must be in the account for 3 months and after that a min of thb 400,000 however 2 or 3 months before extension renewal the 800,000 must be intact.