I have been to SE several times and BKK will give you the most options for getting a connecting flight elsewhere if that is what you need.

You will have to connect thru NRT on DL. You can also use Korean Air and connect via ICN and they have direct flights from there to all over SE Asia. I flew them last year to PNH from ICN.

Personally, prices equal, I would pick KE. I have had better experiences with their service in my travels. However if you are concerned about earning miles for your flights then make sure the KE fare will earn miles on DL as mentioned before.

Enjoy and let us know what you decide!