Most people find a random flight number and random hotel name if they do not already have these. However, proof of both in the past has been asked for and it is as always very embassy dependent.
If proof of hotel is requested at any point, it’s obviously quite easy to just book somewhere to get this. For flights you might want to use onwardflights.com before completing your application to avoid issues of proof being required.
for me they’ve asked for an employment contract as I initially provided them with a letter from my employer saying I was freelance and had permission to work in Thailand.
Apart from that I provided a bank statement showing more than 500k bhat and a copy of my driving license for proof of address. The only extra doc that they have requested so far is the employment contract.
so it would not be at all logical to include the flight from the country you are forced to apply from or possibly some people have nothing useful to say yet still unfortunately add their unnecessary comments just to enrich the the lives of others asking for advice on a page designed especially for that purpose.