I always Fact Check and for this exercise Google Flights provided the following data for 21 November. Instead of quoting prices I'll use percentages
Air Asia (DMK) was the cheapest
Thai Smile (Swampy) was 30% more expensive
Bangkok Airways (Swampy) was between 85% and 288% more expensive depending on time of day
Thai Airways (Swampy) was 377% more expensive