Everything is upto the IO infront of on the day there has never been guaranteed entry it's thailand remember just fly into BKK and domestic to Phuket simple
I think it is a trick question or you are totally delusional I have travelled and visited thailand for a period 3 to 6 months every year for the last 30 years except 2.5 years of the pandemic and have never heard of a 9 day to exit stamp
Yes they can request to see 20,000baht in cash prior to your entry bank statements are not accepted but only been asked once in 25 years of visiting twice every year but it's thailand and no surprises if someone is asked to show it we must remember entry to the kingdom is not a guarantee it's all down to the IO infront of you at time of entry Chokh di