I have flown domestically in the last month and did have to show my passport repeatedly but not at immigration as I would when I'm flying internationally. I asked the immigration officer if I even needed to apply for a new multiple reentry if I didn't anticipate leaving the country. I think she did not understand the question because she just kept repeating, yes, you can apply for multiple entry at the airport.
Just double checking that I do NOT have to leave the country to get my one year extension of stay when I renew this year. My renewal date is Jan 6, 2020. Unfortunately, the date is right around the holidays, so I need to consider this as I do my travel plans.
I probably have the terminology wrong. When I applied last year for the Non-ed, I had to show 500K in my Thai bank account for 30 days before and on the day of the application.