BBC's latest article , including (excerpt):

"The acting president of Airports of Thailand, which runs both facilities, said Don Muang would handle about 140 flights daily.

Thai Airways will operate 30 daily domestic flights out of the old airport, including some flights to the northern city of Chiang Mai.

Eleven Thai Airways routes to popular tourist destinations such as Phuket and Krabi will be kept at Suvarnabhumi to make it easier for passengers connecting to international flights, the airline said in a statement.

Nok Air and One-Two-Go will transfer all of their flights back to the 93-year-old Don Muang."

I kind of like Suvarnabhumi's original name - Nong Ngu Hao, the Swamp of Cobras...