Hello, I want to follow the same route, but I want to apply for a marriage visa after my arrival in Thailand. Do you know if I will need a TM30 too? (For the rest I know the applicable rules).
With a multiple entry tourist visa, easy to apply for before you leave, you can stay at least 6 months in a row (with two allowed borderruns). But that doesn't mean that after returning home you can immediately apply for that visa again. If you do so, appearantly you're not a tourist. You must check if you can get another visa. There are many! If not possible, you must wait until you're 50 years old to get a retirement visa, which had its own rules.