Flight Proof: You're correct that for the DTV application, there's generally no need for proof of flight tickets. However, you're required to provide some details. You can indeed look up a potential flight and enter the airline and flight number. For the "date of departure," if you plan to extend your stay within Thailand, you might enter the date you anticipate leaving Thailand initially or the date of your intended departure from your home country. Remember, this visa allows you to stay for up to 180 days per visit, with the possibility of extending for another 180 days in-country. So, you could input a date that corresponds with your initial planned departure, keeping in mind you can extend later.
Previous Visa Applications:
Thai Visa History: This question generally refers to all types of Thai visas you have applied for in the past, including tourist visas. Whether it's for short-term or long-term stays, if you've applied for any Thai visa before, you should answer "Yes" here. The system is likely looking to understand your history with Thai immigration for processing your application.
Hotel Accommodation:
Accommodation Details: For this part of the application, providing a booking confirmation isn't strictly necessary for the DTV application, but you might need to show proof of where you intend to stay. You can either book a hotel and provide their contact information or, if you plan to stay in a private residence, you could enter the address and perhaps the contact information of the owner or the property management. The phone number field could be for the hotel or property contact. If you're not booking a hotel, you might want to prepare documentation for your alternative accommodation to show during the visa process or when you arrive in Thailand.
Better try to call them, they're very helpful - I applied mine via Athens Embassy using my Maltese resident card last December - holding a spanish passport..