I used Thai Smile Airline during my trip from Bangkok to Siem Reap departing from Suvarnabhumi Airport (BKK) on 21 November 2016. I was in economy class and meal is included in the service.
They have Muslim meal option that is cooked according to Halal rules. You can choose it during the flight booking on their website. They pack the meal nicely with a box and a cloth bag. I still keep the cloth bag until now as souvenir. The on board meal consists of main dish, water, juice, dessert, and you can ask coffee/tea as you wish. The flight was on schedule. Overall I had a nice flight with THAI Smile.
Note: all the pictures are mine.