Originally Posted by jagmeets

You should- no harm asking at checkin.

Lotus is the designated F lounge and Araliya the J lounge, with the former being slightly more comfy and typically less crowded, but still nothing to write home about- both have a bit of food n booze and a basic shower stall.

Both take Priority Pass and I have seen both being closed at times, with the lounge attendants guiding all eligible passengers to the other one.
*EDIT: (irrelevant to the OP, still for completeness) seems that Araliya is no longer a Priority Pass lounge as per PP's page -but then that page doesn't list a shower for Lotus either, and I most definitely had one of the hottest/highest pressure showers I had in a lounge in that dinghy shower stall a couple of weeks back*

I get an invite to Lotus, while my wife gets invited to Araliya, and on asking, they just scribble and sign +1 on my invite (and the attendants take that without any question).

You'll be able to use the supposedly better Sri Lankan lounge once they join OneWorld, hopefully later this year.

PS: your flight makes a quick stop in BKK or SIN- I think the BKK stops don't require you to deplane, while the SIN ones do.