I usually arrive between 3-4 hours for my flight because u can never know about Thai road conditions or if u leave anything behind or the queue conditions at airport.
Having said that I note that your flight is at noon on Sunday so if I am you I will do a 3 hour before flight especially if you are bringing along the whole family.
But I m one who likes to relax n not rush to flights so a longer buffer suits me
How much are you prepared to spend in legal fees? It will take minimum 1.5m to 5m Thai baht and above for whole process. Trial will usually take 2 years from filing of documents.
Weerawong, Tilleke - 2 of top Thai dispute resolution Firm listed in Chambers 500 and Lexisnexus. Pm me if you want referrals