FWIW I am arriving in Singapore, so all flights have to begin and end at Changi.
I was thinking SIN-REP on Silkair, and then REP-BKK-RGN with Bangkok Airways. However, once in Yangon, I cannot book a ticket online out of the country until I am in the country!

I was going to book Silkair RGN-SIN-SOC and then a taxi to Yogyakarta from Solo - but I guess I have to hope my hotel can arrange this for me in Myanmar and then have the places readily available on the flights I want!
Can anyone think of a better way of visiting each of these destinations?