We have three parties flying into BKK from 3 different lands on different airlines. Could you folks recommend a convenient meeting spot? Assuming there is free wifi at the airport.

Why not meet at your hotel rather than trying to meet in the airport? The airport is huge, and there is no where I'd want to hang out after many hours of flying.

Yes, there is free wifi.

We are in the same hotel. We must meet at the airport.

the exit doors from customs are all numbered... pick a door like number 5 or 6 and meet there

the waiting areas are not pleasant, Kathie's idea is better... taxis to bkk hotels are not that expensive 300-400B

The "meeting point" is signed - it is in arrivals

There is some seating there and a couple of convenience stores. Wouldn't want to stay there long.
As pointed out the exits are all numbered.
There are also several (dreadful) eateries there on the arrivals side.
On the bottom floor near the taxis there is a food hall - you could probably wait there for some time - the food is better than in arrivals too.

Thanks folks. Almost there. Wifi shall assist. One last question: is Wat Arun closed for renovations?

We went to Wat Arun 2 days ago, and there are renovations going on, but it was open.