We also returned Wed. night from a 14 day trip and found them very bad on Monday and Tuesday. Even our deet didn't keep us from being majorly chewed. I don't know if the bugs were from the thunder storm that happened a few days earlier, but we didn't have any problems the previous 7 days nor the 3 days that we spent inland in the jungle.
The beach was bug free, but on the pathways around Ramon's and on the west side of the island, they were beasts! Mini golf was a feast for the buggers and the back roads to Taste of Thailand sent our kids in a full sprint for cover. We hovered by the door upon leaving and took our only taxi of the trip to avoid the attack! We saw a pick up truck that appeared to be spraying pesticdes around that area, but not sure if that was what it was doing.
Anyway, nothing that dampered our incredible trip, just a minor something to laugh about now!