@Andy *******
Your advice is wrong . . . The intended departure date is a MANDATORY FIELD. Do you see the red asterixes? You can try just input any date within the 90 days, and pray that the embassy does not ask you for a real, already booked ticket out of Thailand within the 90 days. If they ask, just book a cheap one-way ticket like Air Asia Hat Yai to Kuala Lumpur for 36 Euro. Only in the TDAC digital arrival card, the departure field is NOT mandatory