Well, the easiest solution is to change your open jaw combination, and fly BKK/DMK-MDL then RGN-SIN. Then you could avail yourself of some cheap LCC options. Surely it's just as easy for you to craft a Myanmar itinerary that fits with this, vs your current plan.

Your question isn't solely one about TG though. You can either fly TG OR you can fly cheaper options in/out of Myanmar.