One reason why I don’t fly budget airlines, after all the ++ add ons, I might as well just get a regular airline that gives you luggage allowance and food.
Been going to Thailand for the past 40 years, they never asked for cash of any currency upon arrival at immigration.
The TM6 form is the arrival/departure card, (given to you on the plane) which foreigners are required to fill out with their passport information and other personal and travel information when entering or leaving Thailand.