I always have a very valid reason for not having a return ticket. Needs must you could try flight generator app to show (but not book) an actual itinerary 👍
Depends on how many days you've already stayed in one year, proof of funds apparently now for some, and entry clearance vibes on the day. 60 day TDAC needs applying for 3 days prior to entry. Extend at immigration office for 30 days for 1900 baht