Can I apply for a long-term visa to Thailand without a return flight?

Hi. Most people here are asking about documents related to things like work. I have a different question – flights. Every 1.5-2 months, due to personal matters, I'll need to return to my home country for about a week. So, I need a long-term visa, but my stay in Thailand won't exceed 80/90 days. When applying for a visa, I'm asked to provide a return flight. I have few questions:

1) What if I don't have a return flight yet? I plan to move to Thailand permanently in February next year and have a one-way flight.

2) Does my departure from Thailand have to be a return flight to my home country in Europe, or can it even be to a nearby country in Asia? What if I don't use that flight?

3) What if I buy a return flight and it will be for about two months after my arrival date? Will they still consider me a DTV, or will they force me to apply for a different type of visa?

Which flight did you put into the form? Did they want any confirmation of booking?