Dealing with Khmers in Death Match

Yesterday I lost two games in a row against the same player using Khmers in 1x1 DM.

In the second attempt, I tried to rush him with paladins (Huns) very quick but he managed to keep villagers working and popped out a high number of elephants real fast.

After that, he massed heavy scorpions (the ones that fire two arrows and have extra range). And all the trades were pop and resource ineffective. I Had better eco, but it was impossible to keep up with my military being drained so fast.

I really need a siege onager civ to deal with that?