Where is Koh Lak? Very sad story about your friends, but all too common in that area. I
have a friend who was in Sri Lanka when the tsunami hit. He was in the second story and when the 2nd wave hit, it filled his bedroom with water. He fought for air and had a small pocket near the ceiling. Somehow between the 2nd and the 3rd wave, he managed to break free & ran. Spent 24 hours in a coconut tree, watching bodies and debris float by. When he was finally rescued, he helped with the relief efforts for a few days, then left, ending up in Nepal and a buddhist retreat. I joked, "You headed for high ground?"
"I never thought about it but subconsciously? Yes."
He ended going back to help the family who owned the guest house rebuild (he was a tech guy who cashed out and surfed around the world & had the means to help them.)
To this day, he still has nightmares and wakes in the middle of the night--climbing on the blinds across his windows (they've been replaced several times.)
It's astonishing to hear his story.
When I went to Thailand the last time, I was there 18 months after the tsunami and I was on Koh Phi Phi to see how the relief efforts were coming along. I wrote about it on my blog. Let me know if you want a link.