QR lounge is by far the best in BKK if it's open when you're there. It does match up to JLs late flights but unfamiliar with the KIX departure time and yes you can access it with a J ticket. It is not however a OW Emerald / Sapphire lounge, so no access based on status or guesting based on status.

After that CX lounge is quite good but hours very limited. JL does have the Sakura lounge but it's my least favorite of the OW lounges and only mildly better than some of the contract lounges. All 3, the QR, CX, and JL lounges aren't terribly far from each other.