Yes, there are multiple flights from Bangkok to Tawau for under ฿ 15,009. The cheapest flight booked recently is on Malaysia Airlines for just ฿ 13,058, but on average you can expect to pay ฿ 13,088.
There are no direct flights from Bangkok to Tawau, but Cheapflights can provide you with all the information you need to find the fastest route with the fewest stops.
There are many flights that can get you from Bangkok to Tawau in 20h 55m. Fly via Malaysia Airlines to get the fastest option.
Currently priced at ฿ 13,058, Malaysia Airlines will fly you from Bangkok to Tawau and back. In addition to Malaysia Airlines, many other airlines offer competitively priced options for your trip.