Can I fill in a hypothetical flight number on my visa application for Thailand if I haven't booked my flight yet?

I have some questions about the travel to Thailand part of the application process.

On the application form there is a box to fill in where you will be embarking/flying from into Thailand and a box to fill in the flight number.

If I haven’t already booked my flight to Thailand when submitting the application, is it okay just to fill in with a flight number from the route I’m likely to take?

From reading other posts I understand that they may then ask for an actual flight ticket confirmation with name as part of the supporting documents. Is this always the case? Has anyone applied and not been asked to show this?

And finally, if granted the visa, does it matter if you then change your flight into Thailand from what you put on the application/supporting documents?

I’m applying from my home country (UK) and flying direct from there to Thailand, if that makes any difference.

Thanks in advance for any information you’re able to offer 🙏